As you mentioned, for buffets they would just be able to eat for free. But for those that are not and CS restaurants, I would get a few things that they could share OOP. However, if they are big eaters and you think that they would EACH be able to eat a child's meal, you can get the child's DDP for them.
When my daughter was still 2, we usually shared our meals with her for counter service and table service, she didn't eat that much. Now that's she's 3, we get the child's DDP for her but we find that since she doesn't like the child's menu, we end up going to buffets and cs with no child's menu so that she can eat off the adult's menu.
I know that they stipulate that you cannot get a DDP for anyone under 3, but I don't see a problem with the upgrade. We have been getting the adult DDP for my son since he was 6 since neither of my children eat "typical" children's food. They love the buffets so they don't have to order from the kid's menu. We also choose places like Le Cellier where they can get a steak or Coral Reef where they can get the Mahi Mahi.
I guess what I'm saying is that if I can get the Adult DDP for my 6 year old, you should be able to get the kid's DDP for your 2 year olds. I believe, they just change the age at reservation and make a note on it saying that for the sake of the DDP, my son is 10.