Help me find suitable gifts for my nieces + nephew!!

So, my fiancé has two nieces (13 and 8) and a nephew (10), all of them were very much born before fiancé and I met but he isn’t close to his brother at all and therefore our contact with the kids is minimal (me having only met them twice before!)

We’re spending Xmas this year at my soon-to-be in laws place and my soon-to-be BIL will be there with his family so we need to buy presents!

I have no idea what to get any of them, fiancé is useless and the biggest issue is that they are LOADED (I mean the last time I saw the 13 year old she had a Van Cleef on for a family dog walk) - we’re by no means not comfortable, but these children literally have probably already got a far boujier version of anything I can think to buy them 🤣😭

HELP!!!