gregorykicks

Pull trigger while you can while you learn more about the new plan.  If you want to swap to Unlimited you can but once Ultimate goes away, it's gone.
This is assuming they don't just convert purchased Ultimate plans to Unlimited anyways.   

In most cases, the receipt will specify that a service charge (aka gratuity) is already included in the cover charge you paid. Usually it is specified as either a line item on the receipt, and/or at the very bottom.
You can certainly elect to leave an additional tip if you feel appropriate.

That has already happened.  
https://www.royalcaribbeanblog.com/2019/03/29/royal-caribbean-receives-permission-sail-glacier-bay
 

I'm 4 days to sail and just got an acceptance! Yay- upgrade to Owner's Suite. I'm so happy we'll have extra room. (4 people in any cabin always feels like a lot)

Honestly, between ships and categories I've seen such drastically different minimums and maximums that I can't recommend any specific bids. The best thing to do is see what it would cost you to pay outright for an upgrade, if you're cool with that then do it! Otherwise, bid an amount less than what it would cost you to upgrade that you're comfortable with and see what happens. Remember that your bid is for 2 people! If you bid $100 you'll be charged $200.
I like to bid amounts slightly above "round" numbers (110 instead of 100 for example) just because I think it improves my odds!

So this should be an upgrade to a 1R category room. You'd go from 149 to 260 sq ft which is a HUGE improvement for four people. Plus I think these rooms have the built in bunk beds and curtains so that you can have some level of privacy in areas of the room. I would say you definitely want to bid on this upgrade! In an interior room you'll have two people on beds and two people on beds that pull down from the ceiling over top of the main bed. It's doable, but not fun for a family. 
Remember three things about Royal Up. 
1) Your bid price is per-person for the first two people, so if you bid $40/pp you're bidding $80 total. 
2) The bid arrow telling you "good, better, best" bid or whatever terminology they use is not based on other bids but on the slider for your bid. If you slide to the middle the arrow goes to the middle. It's not really giving you any information about how strong your bid is relative to any other bids. 
3) Just because you can bid doesn't mean the room is even available. I would definitely check the price for just booking that category. See if anything is available and you may just want to pay for the upgrade instead of bidding. 
Good luck!

They will let suite guests and guests who have booked excursions through Royal Caribbean off first. Then it is a free-for-all. Depending on the port, you may have to go through customs once you're off the ship to get into the country (I'm pretty sure you have to do this in Russia). 

Honestly, between ships and categories I've seen such drastically different minimums and maximums that I can't recommend any specific bids. The best thing to do is see what it would cost you to pay outright for an upgrade, if you're cool with that then do it! Otherwise, bid an amount less than what it would cost you to upgrade that you're comfortable with and see what happens. Remember that your bid is for 2 people! If you bid $100 you'll be charged $200.
I like to bid amounts slightly above "round" numbers (110 instead of 100 for example) just because I think it improves my odds!

Oh, I see.  You're in rebound mode ?

They're good. I was just curious.

So this should be an upgrade to a 1R category room. You'd go from 149 to 260 sq ft which is a HUGE improvement for four people. Plus I think these rooms have the built in bunk beds and curtains so that you can have some level of privacy in areas of the room. I would say you definitely want to bid on this upgrade! In an interior room you'll have two people on beds and two people on beds that pull down from the ceiling over top of the main bed. It's doable, but not fun for a family. 
Remember three things about Royal Up. 
1) Your bid price is per-person for the first two people, so if you bid $40/pp you're bidding $80 total. 
2) The bid arrow telling you "good, better, best" bid or whatever terminology they use is not based on other bids but on the slider for your bid. If you slide to the middle the arrow goes to the middle. It's not really giving you any information about how strong your bid is relative to any other bids. 
3) Just because you can bid doesn't mean the room is even available. I would definitely check the price for just booking that category. See if anything is available and you may just want to pay for the upgrade instead of bidding. 
Good luck!

I have 2.
1st story
I work for a national mens clothier.  I go off and buy what I think is a great outfit for my husband.  White/navy blue striped cotton sweater, and navy shorts.  One a.m. we were at the pool and it was kind of chilly, but he knew it would warm up, so he wore this outfit.  It is @ 10 a.m. and he is sleeping on a lounge chair next to me...snoring.  Passengers are walking by and glaring.  Thus, I nudge him so he will stop snoring.  He stops snoring, but they are still walking by and mumbling under their breath.  Huh? I don't get it, why are they looking at him this way.   A few mins later a bar staff member walks up to me and asked if I needed a drink.  I looked at him, looked at my husband and broke out in laughter.  His outfit was almost identical, just different stripe design on the sweater.  I am positive all those passengers thought he was part of the crew sleeping on the job!
2nd story
We as a family (siblings and cousins) decided that we were going to surprise my Mom for her 80th with a cruise.  She got wind and said she was not going.  We (siblings/cousins) decided we were still going and celebrate my Mom's Bday without her.  My brother is a practical joker.  He went to Staples and had a 24x32 picture of my Mom printed up.  In his mind, she was going on this cruise with us no matter what.  He took it with him on the ship, but kept it a secret.  Formal night rolls around and VOILA he pulls this picture out for the photos..  I can't recall the Captain's name, but he was European and needed staff to translate.  There is my brother asking the Captain to take a picture of him holding this huge picture of my Mom.  The captain could not wrap his head around he was being asked to do.  I am pretty sure when he got back to the bridge, he told everyone, now he has seen it all for the photo ops.  
My brother also makes calendars for every family member as a xmas gift.  Every month is a photo.  That yr. her bday month was the picture of the Captain holding this picture of her
 

I'd skip Cozumel, but just because I've been-there-done-that. There is good snorkeling, downtown is decent to explore. I'd consider taxing to the beaches around the East side and bar hopping as well. Have done Xplor in Playa Del Carmen and it was neat if you like the high adventure stuff. I think we picked up a stomach bug there as about a day later half our crew of 8 had some issues. Could have gotten it somewhere else though. 
Roatan wasn't a favorite of mine, but we did really enjoy the Daniel Johnson sloth and monkey. I've heard the snorkeling/scuba is fantastic. 
Costa Maya is like a "Caribbean Mexico Theme Park" when you disembark into the port, which I'm not really into, but we've done Maya Chan both times we've been there and highly recommend it. Not one of the great beaches of the world (curse that sea grass!) but definitely some of the best hospitality, food, and just beach-chill places I've ever been to.