Don’t bother with getting 2 Nintendo switch,
I have 3 children who have consoles.
One has an Xbox , 2 have Nintendo switches, I have a ps5 and ps4.
The ones with Nintendo switches can’t play the same games at the same time. You have to order on both consoles. This includes putting both accounts onto one.
PlayStation allows you to share all games across all consoles. Regarding the account the bought the games is the main account on all consoles.
If you get a Nintendo switch, just get one that you can connect to the tv and an extra set of joy cons.
The best multiplayer games for switch are
Mario kart
Mario party
Super Mario bros
Just dance
Monkey ball
Carnival
Rayman
Sports
(There may be more , but these are my kids favourites ages 9,9&7) xxx