I would definitely encourage you to stay on the west side (gulf coast) vs the east side (Atlantic coast). The Atlantic beaches are smaller and rougher and you're facing east so you miss out on the sunsets.
The gulf coast beaches are some of the best in the US. They have powdered sugar sand and gorgeous sunsets. Anywhere from Clearwater to St. Pete Beach is good and there's tons of lodging options of all kinds and prices as well as restaurants, activities, etc. The Opal Sands in Clearwater is amazing, but a splurge. The Doubletree at North Reddington Beach has amazing balconies right over the beach and further down the Thunderbird is kitschy, old-school fun.
I've found the beaches further south (Siesta Key, Venice Beach, Ft. Myers, Naples, Marco Island) to be a little more challenging to enjoy just because is less available directly beachside. Siesta Key is the most incredible beach, but lined by privately owned condos, same with Venice Beach. Naples has an amazing downtown, but you'll have to take a shuttle to the beach from almost all of the hotels. Marco Island pretty much has the very expensive Hilton on the beach, or the super duper expensive JW Marriott on the beach.
Hope you have a great time!