What to get a 4 year old for birthday? ( & nearly 2 girl, and 5/6 boy)

[LadyOfWaffle]

Friends DSs birthday in May and I really don't know what to get. He is DS2 so they have alot of toys etc., and I want to get him (them) something that won't be at the back of a cupboard in a week. Something for them all would be good (I thought for the garden?) but they have a playhouse, trampoline, slides etc. already. Budget I guess max of £50 . Thanks so much if you can give me ideas

how big is their garden? Would it be possible for them to start their own little vegetable patch? You could buy them the gardening tools, soil, seeds etc to start them off.

Anything super hero related: Ben10, Spidey, Hulk.
My DS is 4 and loves his sandpit (with action figures in it) or his lego

playmobil would be good

and isn't that a lot of money on a birthday present!