I'm going to agree with several others. Bettas aren't hard to keep with basic weekly water changes, vacuuming out waste & a good varied diet. Plants are very helpful for both water quality & betta amusement. They like to snack on plant "goodies" (biofilm & micro-critters).
They have different "personalities", that's part of the fun! If you need a bit more action & have plants &/or hiding places, shrimp can be a nice addition. The betta may eat small shrimp (also fun to watch) but you should be able to keep a colony going. Just something to think about.
A word of warning, most betta splendens (the usual kind) only live for a couple years at best. That can be distressing for kids. But as temporary pets that might not be all bad (I'm not a parent). That can let you "get your feet wet" & see how you like our hobby without too much investment, $$ or emotionally. I hope that's not too brutal to say, I'm trying to give you an honest idea of what to expect in the longer term We're all fish lovers here & we love to help new folks.