Yopu can often get them cheap by booking a week or two before, have a good root around on the web, we paid £500 each for a week in August last year, one of my friends did it for about £470 the week before but sorted his own flights, so it is possible. I hope it all goes well for you
I would go to Cornwall and book the kids on a Surfing coure, yes its fine in the winter, hard work but good fun. Hotels offering good deals too as its quiet Center parks can be good too but lots of walking and expensive. This place in North Wales is excellent http://www.glasfryn.co.uk/ They have a bowling alley, accomodation, some nice beacheds and small towns nearby one with a cinema
Desp for a nice break before dh has next op (cancer) 3 x 15yr olds amuse. Weather is not going to be nice so warm warm accomodation, nr facilities, private hot tub would be a bonus, open to suggestions pls.