This is overwhelming, and maybe someone can make a recommendation.

I have a child that must be infection-free this winter. I have an airstream, and want to take her to north Florida.

Can someone recommend a not-crammed together, nice park near the beach north of Orlando?

Thanks ya'll. I have having a hard time with all the choices.

Below are a number of parks we have on file. You can check each one on this website and call to see if this will do the job for you. Remember all RV parks in FL may be full by now for the winter months. Also parks on the coast will cost you a lot more money than ones inland. We have lots of parks in FL on this website so check other parks as well. Good luck!
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Titusville:
Seasons in the Sun RV Resort.
The Great Outdoors RV Nature & Golf Resort.
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Port Orange:
Daytona Beach Carefree RV Resort
Nova Family Campground
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Ormond Beach:
Coral Sands Inn & RV Resort
Encore Sunshine Holiday Daytona RV Resort

Help us help you by giving us some more information. North Florida is a big area. Do you understand that winter weather in northern Fl may be ok for walking on the beach but probably not often will it be warm enough for beachy activities? If you want warm in the winter you need to go Orlando south. If you want larger spaces and less crowded maybe an area near the "forgotten coast" would suit you better. Check some of the reviews for parks near Carabelle, FL. The further south you go to find warmer weather, the higher the prices and the more crammed together sites will be.

If you read the reviews you can probably find somewhere suitable. But call as early as you can. Most parks are full of snowbirds in the winter.

Infection-free sounds like you want something warmer than north Florida. No runny nose IOW which comes with cold weather.

Start with this map of Florida State Parks
http://floridastateparks.org/findapark/stateparksmap.cfm
and get a map from AAA and locate where the parks are. Don't stay north of Ocala or Orlando because they get freezes. Inland gets colder than the coast.
There is an online reservation system and it gets booked up early because it's the cheapest place to spend a week.

I can suggest Myakka River State Park outside Sarasota FL on the west coast of Florida (south of Tampa). It's a BIG campground with lots of spaces, playground but it's not Disney World, much more of a natural Florida environment. It still gets to 30-40's at night in February though. And during the day you can drive west and spend the day on the beach for the cost of parking.

Start now, the season has started off very busy, lots of people here earlier than last year. Still time to make reservations though. Best of luck.