I've previously lived in Shatin for several years and it's not a bad place to live.
The Shatin New Town Plaza is a pretty good shopping center, right on the KCR rail line, with lots of shops, a fairly decent department store (Seiyu) and a Toys R Us for the kids. There's also a 10 screen cinema and for Brits there's even a Marks & Spencers
There's not a huge choice of Western restaurants, but there's a Ruby Tuesday (American) and a fairly good Indian restaurant as well. As mentioned above, the Swedish restaurant in the big Ikea serves very tasty meatballs. There's also lots of Western fast food places (McDonalds, Deli France, Olivers, Pizza Hut, KFC, Spaghetti House etc).
The Shatin library has a pretty good selection of English books and both the Shatin Central Park and the Penfold Park (inside Racecourse) are nice for walks with small kids.
The only thing Shatin really lacks IMO is nightlife, but it's only a short journey to TST, Wanchai or Lan Kwai Fong for a good cold beer if that's your thing. And yes, there is lots of British, Australian and German beer served in pubs and restaurants in HK as well as that watery stuff that Americans call beer, so getting a good beer is not difficult
Personally, I far prefer living in the New Territories for the fresher air to either the island or Kowloon.