Xbox account question

Hello, I am trying to find a solution. I have an xbox series x and my son has a xbox x. We game share already so we can both enjoy the games I have purchased. Understand is we have to take ownership of each others xbox for this to work. So in other word he is the owner of the xbox series X that I always play and vice versa for his xbox x. What I am trying to figure out is his little friends come over and they want to play together, which is fine by me. But due to them spending tokens earned in my games and such I want a "guest" account, so they do not touch anything in my profile. I have read and tried quest key, but like I said on the xbox I use, my son has ownership. So there is no access to games seeing as I the adult have purchased them all, and I am the ownership on my sons xbox. I tried creating a "guest" account using a new e-mail address and sign in that profile, but it does not work, once logged in it says to purchase game. Is my only solution that my son has to play on my xbox using my profile, and then a person using the "guest" e-mail account on his xbox seeing as I have ownership and all the games on that one? This does work, but my son likes his setup.

:)