Generally, I think Ritz Carltons do pretty well in S Florida and would recommend the following:
RC Naples Beach Resort. True resort hotel, Gulf front, tennis courts, several pools etc. Very god Kids' Club that has a marine facility, which they all seem to love. This is one of RC's "grande dames" and provided you are not there at Xmas/ New Year OR Spring Break time this is an excellent hotel. The Club Floor is very good indeed. The only drawback is that the standard rooms feel quite small (around 425 sq ft) and bathrooms are tiny by modern standards -they have shower in tub, for example.
The RC has another hotel in Naples as well - the Golf hotel. You can still access all the Beach hotel facilities (and use a shuttle to get there) but this hotel is newer and has larger rooms and bathrooms. Having said that, the suites are most unattractive and not worth the spend.
In Sarasota (better beaches than Naples), the RC has a city hotel with an excellent beach club that is about 7 mins' shuttle drive away. However, imho, this hotel's standards are starting to slip and they have lost some of their best staff of late.
Further up the Gulf Coast is a less luxurious but still is a very comfortable hotel, Loews Don Cesar at St Pete's Beach. Good sized suites (at low prices), very pleasant service, 2 pools, great beach location; the sand is like sugar up there.

Over on the Gold Coast, I would also recommend these 2:
RC Fort Lauderdale; not such a resort hotel (but beach front) - fabulous roms and suites, very glossy and glamorous. V good RC service.
RC Key Biscayne - beach front, the largest tennis facility in any hotel in Florida. Good apartments as well as rooms - might be better for a family?

Hope these help. I have stayed in all of these pretty recently.