You don't have to do on line check in @ all, if you don't do it you just go to the regular check in line in the lobby when you get there. But if you prefer to do on line check in (as I do) then, yes, you would need to do it for both. You don't need to do it right @ 10 days, you can wait until you are w/in 10 days for both ressies and do them on the same day one right after the other if you like.