I think there was another thread on this several weeks ago?
Anyway, when I was there with a 6 mo old, they had baby seats for the Character meal resturants (Crystal Palace and Garden Grill) that worked great with DS. Those were the only places I went with him.
But, based on the thread, if I remember correctly, it seems that they have the infant style ones (which work for newborn up) in the Character Meal places, and then MAY have them elsewhere, but up to individual resturant to decide.
They have the wooden ones everywhere, but I can't image a 4 mo old could use that (I know DS could not at 6 mo).
If they do not have an infant style baby seat, then I have heard they may let the stroller in, if it can fit well against the table, etc.