Iselin, NJ Chow
I agree that the Menlo Park Diner on Route 1 South is a solid choice if that's the route you decide to go.
An obvious question is, how old are the kids and how picky are they? There are many chain restaurants in that neck of the woods that might appeal to them, if not to you. The Cheesecake Factory is in the Menlo Park Mall, Five Guys is in the Woodbridge Mall and in between are places like the Bonefish Grill (seafood) and Famous Dave's (barbecue).
It's far from mundane but you might also want to consider Harold's New York Deli for huge and exceptionally good deli sandwiches, as well as many other wonderful selections. Sunday will be pretty busy so be prepared to wait.
If you like thin crust pizza, Nancy's Towhouse in Rahway is a good bet. Not sure though if it's open on Sunday.
I've got the perfect family friendly place for you. Rasoi II, 1567 Oak Tree Rd., Iselin. Large selection of Indian favorites at the buffet; which was outstanding. And, plenty of menu items. Dh & I were there two Sunday's ago and had a wonderful meal.