You need three dips really or colour code by age band
3-6, 7-10, 11-15
Mini torches, stationery, little craft kits, yoyos, bubble wands, flashing bouncy balls, sand critter toys (bean bag toys in shiny bright colours), books (Poundland do Mr Men ones), bath bombs, fun tooth brush (you can get sharks and tigers), bath sponge in a nice shape, little wooden puzzles, nano block mini makes, little playmobil sets, playing cards, top trumps, slinky, Rubik's cube type toy.
Pound shops, B&M/Home Bargains/ Quality Save, Hema, Tiger, Wilko, Ikea and The Works would be my 'go to' places