Where to Live in Winter

My sister and brother in law want to move from London to south Florida next January through March/April. They are both 51 and very financially stable.

My BIL is going to need to fly to NYC probably every other week, so location to airport kinda important. They would also like to be on the beach or really really. close to it. And then have nice restaurants/night life nearby, but not nightclubs/insane crowds.

I'd say $10-15k/month USD is their budget. What neighborhoods would you recommend they look into and why?? Thanks!