Personally, I love DP.
It's a lovely place to live with loads of amenities, loads to do, good transport links, good schools, good clubs, good pubs, good restaurants and a wonderful social life. There is something here for everyone. For all ages and all interests.
Make sure you send the little one to Auntie Mal's nursery and the elder to either St. Andrew's Major CW school or Dinas Powys Infants School on Cardiff Road (http://www.dinaspowysis.co.uk/). BOTH seem to be turning out great kids and results! I have a daughter of 6.5 and she went to Mal's and then to St. Andrews. I couldn't be more happy with the way they have looked after her!
I hope none of the postings on the discussion forum have given you a bad impression. In fact i would say that the fact that people are not on here discussing more problems than they do is actually a good sign!
I would say the best thing to do is come down to Cardiff for the weekend and have a look around.
You need to speak to Mike Baker at Peter Mulchay Estate Agents (029 20515123) and John Coombes (02920 513151 http://www.joncoombes.co.uk/ ) as they handle pretty much 95% of the property in DP.
Oh, and i'm pretty sure there is an orchestra hiding somewhere in the village. I remember there being a performance recently. Good for the missus ;)
Trev