You mention budgeting, so here are my affordable suggestions! (You can see I only ever shop in about 4 different shops too.....)
he girls (and possibly the boys) might like some cute stationery - don't know if you have a Kenji store near you for example but they do really sweet little pens, notebooks, and also things like key rings and pin badges etc, which are cheaper than you would expect and really nice designs I think.
Face packs, definitely for the girls - and I have to say my ex husband loved them too, and so does my adult step-son.... Primark have a big range and are cheap, Superdrug also.
Poundland also do some foot masks - foot peels? - that don't dissolve your feet away and are surprisingly effective.
Poundland also have a great range of nail varnishes.....
Poundland fragrances are actually pretty nice. I got my mom one with a flower on the lid that is lovely - I always borrow it when I go round.
Poundland sweets - they have an excellent range - the fake Toblerone (think it's called Twin Peaks?) is really nice.....
Everybody likes socks. Again I the Kenji store is good for these?
Second hand books from charity shops? You often find things that haven't even been opened - often 2 or 3 for a pound.....
Chocolate stirrers from somewhere like Lidl or Aldi?