Jeni

There are plenty of videos on this blog or you can search this blog on YouTube and find a ton that @Matt has done. 
Welcome back to cruising and to the boards

In addition to the EXTRA helpful RCB videos I also recommend cruise vlogs (videos by cruisers taken while they are on the ship) from Paro DeeJay and/or JJ Cruise. I think they offer really good views of the ships they're on and give great advice on things you may not know you don't know. (especially on an Oasis class, which I swear has so many silent perks!)

There is even a Hallmark movie about Harmony....

We flew in the day before (7/16) and we used GoPort for airport to hotel and hotel to port and then port back to airport.  It worked like a charm!  On the shuttle (it was a big bus) from the hotel to port and port to airport it was a great experience.  We had 8 people in our group.

When the all inclusive beverages aren't included in my cruise cost, I get the refreshment package.  Well worth it.  I drink a lot sparkling water on a cruise.  We're not big coffee drinkers, maybe one cup in the AM, so we don't get it for coffee.  
My recommendation, buy the package now and keep an eye open for a sale of it between now and cruise day (or whatever the drop dead date is).  If the price gets lower, than buy the lower priced package and cancel the higher priced one, you'll get a refund in just a few day on your C.C.  It's easy peasy.  

Correct. Same (or close enough to the same) as it was pre-covid

So we need to register our kiddo at AO when we first board right?  But then we can drop off and pick up whenever?  Do not need scheduled times?  Going on Harmony on October and also cannot find any info on AO for this yet. 

Yes there is and it's usually around $7-8 but you can ask for the drink of the day without the souvenir cup and bring price down a few dollars.

I was on Harmony in March and had NONE of those issues.  Because I did a little research in the past, I know room service costs $7.95 for anything beyond the continental breakfast. In fact it’s WRITTEN ON THE MENU!!  The cost of drinks is discussed to death.  If you don’t want to pay individually BUY A PACKAGE.  MTD dining allows you to make reservations in advance. DO SO!  And I slept like a baby on a very comfortable mattress.

Current protocols requires 12 and over to be vaccinated.  An eight year old is not required to be vaxxed and will be allowed to sail based on current protocols.  If anything those protocols may ease before October but even if they don't you appear to meet the current requirements.  

We just sailed on Allure of the Seas in June with two kids under 12 who are not vaxxed.
The process was pretty straight forward:
Got a PCR test for them on Thursday (three days) before our Saturday embarkation. Printed that out and brought it with us. At the cruise terminal we joined the special line for kids under 12, showed them our PCR test, and kids received an "antigen" sticker indicating they needed a test. Each kid got a quick nasal swab from the testing technician and we proceeded to check-in (showed our boarding documents, health questionnaire etc.) We waited about 15 minutes upstairs in the cruise terminal before we got the text/email with the test results. Showed the emailed results to the employees in the waiting area, and again before actually stepping foot on the gangplank
While on the cruise we were notified that they needed to be tested again before the cruise was over, so on the second to last day we took them to the 4th deck main dining area and snaked around to a testing area where they again both got a quick swab. We were told "no news is good news" and didn't hear anything else about the tests after that.