The Special Needs is for Senior or overweight pups. It is not grain free but I think it only has a couple of grains and they are the grains that are the easiest to digest...
You could just go with a Grain Inclusive one and take just a teeny bit of kibble out and replace it with a few Green Beans. Green Beans are great for overweight pups... my Vet said that basically, they burn them off by the time they finish chewing them.
I have even heard of some people putting their overweight pups on a greenbean diet.