I moved from the very South to Yorkshire many years ago following a really awful divorce as I wanted a fresh start and had a great work opportunity. It is only Covid and the lockdowns that have given any reason for regret as my family in the South seem so far away now. In normal circumstances no regrets at all. Moved with teens who settled really well but (sadly) both returned south for Uni. Obviously this makes it even harder being up here, and long term I'm not sure all the benefits outweigh the greater contact I'd have if I was nearer them (in non-Covid times).
The biggest things I noticed for the better are the cheaper housing, whether bought or rented, amazing amounts of unspoilt countryside, chattier and friendlier communities and all the people I met had more seemingly expendable income largely due to far cheaper housing costs. Most of the working age people I know in the South are spending ridiculous amounts for decent houses (again whether rented or mortgaged).
The weather is the biggest downside - it IS noticeably colder even on the hottest summer days and I'm very rarely warm in the winter!
At the age your DC are, and being in a stable relationship, I'd say go for it - and go as far North as you can as it just gets better and better in terms of scenery, beaches, small towns/communities, green space and fabulous cities. However, if you will find distance from existing family or friends difficult, or if your relationship isn't solid and happy, I'd urge caution as once here it will be very difficult to go back IMO. I had to have special Court granted permission to move the teens that far from their dad and had to pay all the costs of every other weekend contact. So if you were to split in the future and wanted to go back South, it's not that straightforward.
Over the last five years I've met loads of Southerners who've made the move, more and more are seeing the positives.
Very best of luck - keep us updated!