I never do a dining plan, but my kids are a similar age to yours. Our last trip was in 2015, the boy was 5, the girl was 3. We usually do 2 days at MK and 1 at EPCOT. We try to aim for a sit down dinner to rest in AC for an hour or so. Generally, at MK we want lunch to be quick and flexible. The EPCOT pace is so slow that sometimes we do get lunch reservations, sometimes we wing it.
Our next trip is this March, and I already have a ton of ADR's. For dinner, Chef Mickey's, Crystal Palace, Akershus, and Artist Point. We only have one TS lunch ADR, Marrakesh.
In March 2015 we did table service for dinner every night (Bongo's, Crystal Palace, Akershus, Mickey's Backyard BBQ), generally quick service for lunch (Columbia Harbour House, Pinocchio's Village Haus) and maybe Marrakesh TS for lunch too. Breakfast was either quick service in the park we were at or the table service buffet at our resort (Trail's End).
I think when the kids were 4 and 2 we did Bongo's, Crystal Palace, Marrakesh and Hoop Dee Doo Revue for table service. Lunch was Be Our Guest with fastpasses (weird trial thingy), San Angel Inn table service, Pinocchio's Village Haus.
So, no, it's not weird to have two or even three TS meals if you expect the day to have a slow pace.