When our little ones were little we put them in the dinette. As one reply said, at that age facing rear is recommended. Motorhomes aren't usually too conducive to using car seats but that is the closest you can get to what is recommended as the couch will have that facing sideways.
One thing that National says to do is to stow the dinette table lest it become a missile in a crash. Honestly we never did that. Probably is a good idea if you are worried about it though.
Hope that helps.
Tony, Alisa, Bobby & Anika
2007 National Sea Breeze 1350