OK I will try to start out with the positive. My family relocated to Florida from San Francisco Bay Area when I was 13.
Pros:
Close to Sea World, Disney World and Busch Gardens. Beautiful beaches. Swimming a good 9 months out of the year. The Space Center was cool. It is sunny most of the time and the thunder and lightening storms are very intense, only a pro if you like those, a definite con if you don't. Dolphins and manatees!
As you can see I have a very short list. I got the heck outta Fla as soon as I could and left when I was 19. I did not like Florida, and yes I experienced serious culture shock, literally. Theater and museums are almost non existant. Seasons consist of Hot and Humid. Flat, flat, flat. I think I missed topography in the landscape more than anything. Someone who loves mountains does not belong below sea level! BUGS!! OK Grandson may think that is a pro, I did not. The cockroaches are the size of small dogs (OK I am slightly exaggerating) and they fly! You cannot live down there without having a monthly service come to spray for bugs! If you don't spray you WILL be over run by them. The spiders are huge, varied and some of them build webs that can span across an entire street!! I won't even mention the mosquitos. Suffice to say most towns have to spray. Snakes! loads of em and most of em are poisonous. We had classes in school so we could easily and quickly ID the venomous varieties.
Hopefully this will be a great opportunity for your DSIL and your DD and DGS will adapt and not find Fla. as awful as I did. Obviously tons of people love it down there. I was not one of them. But I do have some fond memories of the area.