Congratulations on the new baby!!! And baby's first trip
that's exciting!! We normally go out once a week.....perhaps the difference was the wait at the restaurants we chose. At home we will go to normal places to eat TS meals.....Texas Roadhouse etc. , Our normal in and out time is 40-45 minutes. At Disney we ate at our normal favorites ( Teppan Edo, Yachtsmsn, Narcoossee, Le Cellier etc. ) I think DD was complacent for the first 30 minutes of the meal, but after that she got whiny. So about the same amount of time that she does well at restaurants at home, but meals seemed to take longer at those restaurants. For our upcoming trip I am making sure to not schedule anywhere near nap time!
I am sure your DS will be fine, he is going to have an amazing first trip. For character meals you can always walk him around to see new things until they come to your table....my daughter didn't like to be ' stagnant' or just sitting for an hour. Good luck, it will go well!