Lots of people suggesting PS5 because of the exclusives, which I don’t think a 7 or 9 year old would really care about except maybe Spider-Man.
Xbox has a lot of good, kid friendly MP games they can play with their friends—Halo, Sea of Thieves(safer seas coming in a few weeks), Grounded, Forza Horizon….plus gamepass. In my friend group with similar age kids to yours (3-9) we all have Xbox & Switch for the kids.
That said, I would ask the parents and see what, if any, their friends have and just do the same.
Skiing in Tribes. Biggest exploit ever that fundamentally changed how the game is played so much that it’s now a staple of the series.