I didn't get any responses, but there seemed to be quite a few views, so I thought I'd do a quick follow-up post.
We had a really nice time at the HRC in Siesta Key. The staff is great and very helpful. Because we are a younger family, we sometimes feel a bit out of place at the higher end properties, but everyone was really friendly and really tried to make us feel welcome.
So here are my recommendations for others in the future:
1) There are Bikes, Kayaks, and Stand Up Paddleboards available for use. We never had any trouble using these items. The bikes are not made for riding on the beach (but they are pretty good bikes for riding on the street). There are some life jackets available, and bike helmets too.
2) The breakfast fits the theme really well (it feels beach-y sophisticated). There is fresh fruit (mangos, grapefuit), a variety of breads, and some proteins (hard boiled eggs, lunch meat, etc). In past stays at the Hyatt Grand Aspen the breakfast just seemed out of place (in my most recent stay they have a bowl of fresh fruit in the area where they had served breakfast previously).
3) As far as activities are concerned, we had a really nice time just lounging on the beach and playing in the ocean, and that worked out great. With older kids, I would have definitely set aside some time to go on some longer kayak trips, and would have considered some other activities (like parasailing).
4) I'm not a seafood person, so we didn't explore restaurants much. I really liked their grills, and would definitely plan on grilling out most nights in the future. Had I been better prepared, I would have bought stuff for sandwiches and used the cooler to take those down to the beach.
5) My in laws are seafood people, and we tried to get some fresh seafood at the fish market that is very close to the HRC (Big Water Fish Market), but none of it looked all that appealing and didn't appear to be local (salmon, etc).
6) You may self-park or valet park. We opted for self parking (since we have three in car seats, we don't like getting in other people's way).
7) I wasn't a big fan of Siesta Key Village -- there wasn't really anything wrong with it, it just didn't have much that appealed to us (lots of touristy shops). Older kids would probably enjoy those shops (and the dozen or so ice cream shops).
8) My wife got attacked by mosquitoes or no-see-ums...she's got tons of bites all over her arms and legs. I wish we would have prepared a bit better for that.
9) It was incredibly hot, but the umbrellas made sitting on the beach very nice (along with a nice sea breeze).
When I have some free time, I'll write up a review.