S.C.
You already have great suggestions, and it sounds almost like you already know what you want to do, sort of. My 7 almost 8 year old son is an official volunteer at the rehab and nursing center. He goes in and reads or plays ball, or just visits with the elders living there. It made their day for sure! One lady didn't smile all day until I asked her if she wanted to play ball w/ my son... She didn't stop smiling.
Also, local animal shelters love it when kids come in even just to play with the animals. It gets the animals used to people, and kids especially, and helps them be socialized and more adoptable.
Then you can also put the little guy in a stroller and go for a walk and pick up trash on the side of the road. Just watch out for broken bottles...
Um... Oh, you can maybe make cookies or something and go to an elderly neighbors house to visit.
It is very nice of you to want to help people and teach your children to have a helpful, caring heart too.