I'm in the US, in California. We moved back to the UK when we had kids but ended up hating it, especially the schooling which seems to be really inflexible. We moved back to the US when the kids were in primary.
I do think the weather can help make for a great lifestyle and that may be true in Florida too. Neither the US nor the UK do great on kids happiness and wellbeing outcomes compared to other OECD countries, but the US does tend to just pip the UK and one thing I really notice is that kids aren't disliked and considered a nuisance in the US the way they are in the UK.
However, we're well off. Can afford to live in one of the more expensive places, can get them into good schools where we don't worry about guns, have good health care and vacations. We also had a significant support network from when we lived here before.
I think it's worth considering. Many people love it (including me!). Americans are generally more positive and outgoing than Brits and that can be addictive without you even realising it. If you do find somethings about the US attractive and decide to try, you need to plan carefully to get yourself integrated into the community. That means your husband supporting you in making your own friends, developing your career at least as much as he develops his, using his friends and family to help you, etc. It's much harder to do this as a married woman with kids than as a free and single 20 something, especially if your role in the family is to carry more of the domestic load.
In your shoes, if you're unsure about it, I think you should
be very reluctant to move countries in case you change your mind or your marriage deteriorates (which is not something to dismiss if you are moving country) and you end up stuck in a country you have no other ties to in order to stay with your kids as you would be unlikely to be able to insist on them going back to the UK with you if their father disagreed.