Have your son and his friend go around and offer to rake people's yards for $10 or $15. They will need two rakes, tarp to rake leaves onto and then drag to edge of yard for pickup. Or they can put the leaves in yard waste bags that the homeowner provides them if that is how it is done in your neighborhood.
Do any of the neighbors need a dog sitter. Make-up a flyer explaning the trip and the need to raise funds. Put on there a list of jobs the boys are willing to do. Like watch/feed animals while people are away on trips, raking leaves, shoveling snow on walks, walking dogs, walking kids home from the bus stop, washing cars, sweeping out the garage of salt in the winter, staking wood for fireplaces, getting decorations out of the attic, washing the dog....all services should be done at a very reasonable price to get interest. They will have to work hard, but it will be worth it in the long run.
Good luck!!!
Maybe even a paper route if they let kids do them these days. My brother had one when he was in middle school and he made good money.
Most of these will require a parent to supervise or even provide transportation at times. But it is a good lesson to learn.
They can also collect aluminum cans from all the neighbors. They can smash them in the garage and then have an adult take them to a recycling center every month with their collection.
Have the boys make boxes for neighbors that will agree to donate their aluminum cans to them. They will need to line them with garbage bags and go around every week to collect.
Hope those ideas helped. Growing up my brothers and I were always doing something to earn extra cash. My dad was military and we didn't make much money so we learned to hussle.
Oh, the boys could clean leaves out of peoples pools and even help tear them down for winter.
They need to put on the flyer that they are willing to help with any household chore for say $2 an hour. It isn't much, but people can't afford much either.
