A good destination in Florida for Christmas vacation is Naples Florida. Naples is located in Southwest Florida, on the shores of the Gulf of Mexico.
Naples climate is mild year round and gets lots of sunshine hours. Although this area is very upscale, you can find quite reasonable priced accommodations too. There's beach front resorts and lots of hotels and condos to choose from away from the beach too. Vacation rentals are also very popular in Naples.
There's plenty to do for families and couples. The gorgeous white sand beaches are the main focus of the area. There's lots of restaurants in a variety of price ranges, too.
Naples is known to be a very safe area too, which is important when traveling.

" I'd be happy with jeans and a t-shirt weather or even jeans and a hoodie"

If you don't expect to swim in the water, the panhandle of Florida has gorgeous white sand beaches and you can get great deals on houses. Christmas week will be pricier than other weeks but probably less than south Florida. We stayed at Seacrest in a gorgeous house in January and loved it. It will be cooler than south Florida but much warmer than Nebraska.
www.30a.com

The panhandle is lovely, but Panama City will be 10 degrees colder on average than Sarasota in December... and the water will be much too cold even for splashing kiddies.

The panhandle IS lovely.
Yes, PCB will be colder on average than Sarasota.

"...... and the water will be much too cold even for splashing kiddies"

Do not agree.
It may be. It may not be. It could be 64 degrees (vs 74 in Sarasota) but it could be 80 degrees. Some of my favorite photos are the kiddos splashing in the Atlantic on Dec 31st. The gulf will be warmer.

Based on the OP's most recent post (about jeans and hoodies), the Panhandle is a viable option.

80 in Sarasota in December would be slightly above average. 80 in the panhandle would be highly unusual. Has it ever happened? Sure. But I wouldn't bet my own money on it.

Thankfully, I'm sure the OP will figure it out for herself.

But I do enjoy hearing about Florida weather from people who don't live in Florida!

I'm almost afraid to comment but here it goes. For what it's worth we've been going to Sanibel for the past 8 years either the week before Christmas or the week after. Only 1 time was it too cold for it to be enjoyable outside after sundown. Not one time did we ever have rain any of the days we were there. Did we go swimming each year? No, but every single year we go for long walks on the shore, build sand castles with the kids, fly kites by the ocean and take bike rides to the lighthouse. Can florida have cold snaps? Of course just as well as we can have heat waves. The op specifically asked about locations in Florida, why try to dissuade her? Relax, Its not such a bad idea.

Dull as dishwater.

Enjoy your holiday trip, becky!

Excellent post, mabella.

The WDW mention was qualified about expense, but worth adding that Christmas week at the parks is annual peak crowds. Parks often close at 9 or 10 am from overload crowds. Pricing is accordingly high season. Hotels, restaurants, and highways are at capacity. If that's your scene, great. If it's not, be aware.

Putting weather aside, we like the southern Gulf Coast because of the beach, fewer people and lots of great nature reserves. Anywhere between Sarasota and Naples is nice and has lots to do. Sarasota, in addition to great beaches, has the Selby Gardens (good kids' section) and an aquarium, and Myakka State Park (alligators, boat rides, canopy walks) inland. Near Naples is the Everglades, Corkscrew Swamp and Sanibel/Captiva islands. I think it has a good kids or science museum, too (worth checking).

We go to this area every year for a few weeks at Christmas and just love it. Sometimes we wear sweatshirts and sometimes shorts, but either way it is lovely and very green and balmy compared to up north.

For my experience, there is no place quite like Sanibel Island. The beach has the third best shelling in the WORLD. Kids can get into collecting and learning about shells. As for nature, the "Ding" Darling NWR is a great experience for grown-ups and kids alike. And the island is very kid friendly, more so than this space allows. As for where to stay, my biased recommendation is West Wind Inn. It's on the beach. The pool is heated. There's onsite dining. It's so dark at night that the kids can lie down on the grass and get lost in the stars.

bookmarking for planning a Christmas trip........thanks for all the great recommendations so far!

As I mentioned upthread, the "cold snap" this year in Fort Lauderdale happened one morning when it got into the 40's for about an hour.

Indeed! We go down to see family in the Deerfield Beach area when it's cold in Orlando.... We show up in jeans and they are in shorts, saying "How cold IS it up there??" It's probably between 45-70, so we are bundled up. They are more like 80. LOL

"Cold" is relative..........like the OP, I live in an area where it's literally freezing in December. Low 60's/high 50's seems like a heat wave.