I got married when I was 29.

DH's parents gave us $2,000 which we brought our rings with (size U for him so that's why so expensive). My mum brought the cake and Dad a piece of furniture we wanted, and that was it for contributions from the family towards our wedding.

I suggest cash would be best as a gift unless there's something they actually WANT.

Put it this way- what would you give another child of yours? To be fair, it should be the same for all siblings, no matter what the situation. Otherwise it might end up biting you back later.