This is a toughie!
It all depends on what you want to bring home and where you want to eat!
So for myself and DS I would budget 30 per night for my dinner (including a drink with dinner and a cocktail after) and 15 for DS. For lunch I'd say 25 would cover us both and I generally buy the kids a jumper each (25) a tshirt each (15) and a toy (25 each) so for me and DS that would be::
Dinner 180 > 45 x 4 (no dinner on last day) > Dinners would be at Cafe Mickey, hotel buffets etc.
Lunch 125 > 25 x 5 > Lunches would be in the park, like Caseys or Toad Hall.
Presents 130 > two jumpers, tshirts and toys.
So thats 435. I would also spend about another 200 on bits and pieces like popcorn, drinks, pins, magnets for the grannies and sweets for nieces and nephews.
So we'll say I'd bring 650 and have another 100 just incase money.
My shareholders card helps a lot and we always end up spending loads on extras that catch our eye.
In January I plan to be more strict on spending and am bringing 750 to cover 5 days for myself and DS.
I think it would be easy to save a few quid by getting bits from the shop in the station for lunch and by going for McDonalds a couple of nights, especially if you've had a bigger lunch.