Help on cooking frozen casserole

I am making a hashbrown casserole tonight, and want to put it in those small foil dishes instead of cooking it in one large pan, like I normally do if we have company, and like I used to when I was still married. Now it's just DS16 and me, and I am trying to stay low-carb, so no yummy hashbrown casserole for me.  If I have it in those smaller/medium foil containers in the freezer, my son can cook one up himself for lunch or whenever. 

First question: should I cook the casserole before putting it in the containers and freezing?  So that he would be cooking it from a frozen state.  Or, should I cook it in the foil containers, and then after it's cooled down freeze them?  In that case, he would be reheating it from a frozen state. 

Second question:  how long, what temperature should we be cooking these from frozen, in a convection oven?

Thanks, I am not a very experienced cook!