If you don't mind them goggling at a pc screen, get them a decent adventure game. I have just finished "Destination Treasure Island" - utterly charming, and some decent puzzles. The 12yo in particular would love it. Another enchanting game is "Syberia".
ha ha all good ideas got the little bleeders i mean darlings to help give the house a good spring clean in the end but thanks for all the advise everyone x