Noob dad has questions on what to buy for kids

Hey all - sorry if these questions are very basic. I have absolutely zero console experience. I want to buy one Switch OLED for my 2 boys, for a roadtrip. The idea would be to use the desktop mode so they can play together, and also gets them the option to play single-player games one at a time.

Questions:

• Do I need to buy more controllers? Are the 2 included enough for most 2-player games?
• Can the OLED be charged in desktop mode? I read that the V1 cannot because the USB port is on the bottom edge.
• What games are fun for 10-14 year olds that don't play Call of Duty and that sort? Is the included Mario Kart okay, or should I get some particular game bundle?