When I have had fun kids dinners to plan where there are boys and girls, I try to go somewhere that is not too princess-oriented, so that the boys don't feel left out. And with a 1 and 4 year old, I would try to keep it in near the Magic Kingdom, or at most a monorail or boat ride away, so that it is easy to get to. A few suggestions are;
I know that you said in a park, but the Contemporary and Wilderness Lodge resorts are all a quick jump away from the Magic Kingdom, so really you should consider them as well. Here are my detailed observations;
Biergarten is fun, as a German oomp-pa-pa band creates a fun atmosphere, and the kids buffet selections are good if they don't want to try German cuisine. Chef Mickey's has good buffet food, and a cool setting with Mickey and all his friends. And the Whispering Canyon Cafe provides some great western themed fun that is not as theatrical as the more famous Hoop Dee Doo review.
I am glad to provide further recommendations if you ask me directly. Just let me know about the kid's interest when you ask me from my bio page.
Have a delicious vacation!