Thanks for everyone's feedback - it's been very helpful, and nice to get a sense of what others are doing. I tend to be a planner, but think I sometimes overplan things. But with a family of 4, every penny counts more often than not. I've been pricing my options and this is what I have found thus far:
VIP Executive limo quoted me $240rt for a minivan shuttle for 4, which includes all taxes, port fees, tolls, etc, and includes a grocery stop if we wish.
Happy Limo (Mousesavers recommended) looks to be about $235rt for a town car. Like VIP, price includes all taxes, fees, tolls, etc.
For rental cars, I'm looking at Hertz. I know they're not the cheapest out there, but they are right next door to the hotel we are staying at the Cape pre-cruise, plus I am a AAA member and can usually get a discount on a rental. Pricing as of right now, for a full-size, one-way rental is $251.37: $165.32 out, and $86.05 back. That includes a free upgrade code and a mousesavers code. I think the reason it is so high on the outbound rental is because Hertz (Cape location) closes around 4-5pm on the Saturday we arrive, and unfortunately we arrive late (9-10pm ish), so they are charging me for an overnight rental. Other rental companies in the area are showing they close around similar times. I suspect that price may drop as we get closer to the depart date, but.... And this price doesn't include tolls (I have my own Sunpass), fuel, etc.
So I think I am going to reserve with a limo service, but keep watching the rental prices and checking codes. If I see a significant drop in rental price, I can always cancel my reservation with the limo company. Has anyone had any experience with the above listed limo services and/or recommend any others? I've picked those two because of reviews on other sites.
Thanks again! With almost 4 feet of snow on the ground, and a winter storm hitting here every other day, I am VERY ready for a cruise!