Kicking Explained

I am wondering how kicking works. I have a few guest players who come in once in a blue moon. If I kick them from the game will I be able to invite them again or do I have to leave them permanently?? 

You will be able to invite them again.  Two things happen when you kick a player: They no longer have access to the game. The join link for the game changes. If you copy the (new) join link and send it to them, they will again become part of the game. One thing to be aware of is that anyone that has not yet joined your game and has received the join link before you kicked someone will require a new join link.