Should I cancel some of my interviews/withdraw from some of my schools after A?

I'm really thankful to be in this situation, but I wanted to know what was the best course of action. I was lucky enough to receive an acceptance yesterday, and while it's not at my top choice, I have IIs for two schools which have been scheduled in the next two weeks, where I know I won't attend because of this A. I am wondering if I should immediately call/email the other two schools to decline and hope they can interview someone else, or if it would be too late for that.

Also, my other question is whether I should withdraw all the schools I know I won't attend (including ones I haven't heard about II from) or just decline further IIs from schools I won't attend.

Thanks for the advice!