Go to Naples!! I may be biased because it's my hometown, but it's fabulous at Christmas time. Absolutely fabulous.

We went to LegoLand last January. It was a cool weekend and the place was empty. We really enjoyed it.

It's going to be 85 in Tampa all of next week!

So, I live right near Tampa now (moved here from DC). It may or may not be cold. The weather really varies. But there's still tons to do.

Here's a few suggestions just off the top of my head:

A big thing that time of year is going to see manatees. They are magical. There are two places you can go see a whole ton of them in the area.

Crystal River: https://www.facebook.com/VisitCitrus/?fref=ts

And Apollo Beach: http://www.tampaelectric.com/company/mvc/

Clearwater is pretty boring (I think) but you can go do some stuff in the area. There's the Tampa zoo, which is nice. (And not abusive!)

Big Cat Rescue, like someone else suggested: https://bigcatrescue.org/

Disney's just about an hour away, too, so you can certainly spend a couple of days doing that.

It's really nice around here, even in the winter.

OP, I am not sure why you would want to go away from Clearwater. Sure you won't be able to swim but you you can still do beach activities - little ones love making sand castles and playing with a ball or just running. You can do the aquarium, children's museum, dolphin watching.

The temperature in December in Clearwater is certainly going to be better than in DC! A 74 degree high is certainly fine for the beach.

http://www.accuweather.com/en/us/clearwater-fl/33755/month/332295?monyr=12/01/2016

Legoland is about an hour from Busch Gardens, might be fun and def,. warmer because it is inland.

I came across this thread while searching for something - not sure if you are still checking, OP. Sorry for your loss. I was in a similar situation last year and we ended up going to Sarasota (maybe others can chime in) but that's a great place to go instead of staying in Clearwater. And it will be about 10 degrees warmer than Clearwater. Not beach activity (PPs are right you have go further south) but if you didn't want to drive 3+ hrs then this is a good option as it is only an hour away which may be doable with your little one even on the day you fly.

Avoid the ringling mansion and show but there is the big cat sanctuary, jungle gardens, children's garden and a really nice aquarium. Also we did a nice picnic at a mangrove park (forget the name). That should be a good 3-4days.