This is a great idea, but maybe it would be worth considering Linux servers? Not only cheaper, but in my opinion it's easier to maintain and if there's any problem- you can depend on user feedback and help
You cannot be online with the same account on the same game with 2 consoles.
You can however be online with two different accounts on two consoles using a digital game that you only bought one time. Thanks to that they can play 2 seperate games and everything should be fine. You have to set up which Switch is primary and which is secondary