Unlike most people here, I do not find the DDP worth it. Like you, I typically spend less than $50 day for me and my DS on food. We like to spend more on the souveniers, entertainment, recreation and tours -- the things that make a vacation in Disney unlike anywhere else! We are not big breakfast eaters so a croissant or something from the bakery is just perfect. We tend to eat a larger lunch and a smaller, light dinner. There's nothing worse than being "logey" from too much food! In addition, we also bring our own snacks with us, whether it's fresh fruit or cereal bars. Don't get me wrong, we do buy snacks and food in the parks and make ADRs for our must-eats, such as character dining, etc., but when we average it out, it is still just not worth the extra money. I think if I was on the DDP, I'd be eating more since I wouldn't want to "waste" my hard earned money. Don't forget that your children can munch off your own plates too, being the ages they are. My son, 5, still does that! IMO, you have to ask yourself, can you, with a 1 and 2 year old, realistically include the fine dining experiences the DDP offers?
Just MHO. Either way, you'll have a great time.
Congratulations!