Don’t do joint presents – I always hated joint presents with siblings unless it is something “big” like others have listed below, tramp, swings, X-box etc that would be fine.
We’ve tried to go “old school” with presents this Xmas gone and the kids got hula hoops, elastics, skipping ropes, frisbees etc. Lots of outdoor stuff for them to play with. Was a good hit.

if you will spend a fair amount, make it a family toy. swings, tramps, play equipment or playstation for example

A trampoline with a net so the kids can share,a princess cubby house for all of them,a pretty costume to dress up in & dance around in,for each child.And a swimming pool with swimming accessories,floaties,noodles ,just a small one to fill up when needed.