I grew up in Broadstairs and regularly go back to visit my parents. It's a very mixed bag. I've also lived in London, so I'm kind of the opposite of a DFL!
The beaches are gorgeous, and wonderful with young children. However, those children grow up, and there is not a whole lot else to do in the area. I struggle to find things to do with my 15 year old DS when we go and visit. In the summer the beaches are rammed (we never went down on the beach in peak holiday times). Can be pretty bleak in the winter, but that's the deal with any British seaside town.
I went to Dane Court - it's a good school. But the options if your children don't get in are not so great. Just be aware that there are no true comprehensives in the area, as the top 20 per cent are creamed off into the Grammars. That's like having all the top sets missing at the non-grammars. Check out the two Broadstairs high schools (Charles Dickens and St George's) as well as Dane Court, and then see if you are still comfortable with secondary provision in the area. My sister went to St Georges, and had a very different school experience to me and my brothers at Dane Court. The Kent system is horribly divisive and has led to self esteem issues in my sister, as she feels like "the thick one" (she's not).
I'm afraid to say you won't be escaping crime and drug addiction. Parts of Thanet are pretty deprived, and although the centre of Broadstairs has a pretty chocolate box veneer, there is a lot of poverty in the wider area. Thanet is surprisingly isolated, and social mobility is poor - and not helped by the grammar system.
Community - well that's like anywhere really, it's what you make it. Thanet locals can be very parochial, and well, it's the area Nigel Farage chose to stand for election, which says a lot...