There is NOTHING wrong with a friendship with younger folks. It is good you can teach them things that they didn't get taught by their parents or other elders in their own family. Don't let others "dirty" minds make you question your actions. You know that your aim is wholesome. Sounds like those "kids" are lucky to know you. P.S. If that "dirty" mind is your wife....take her along too. Let her know there is nothing to fear from your relationship with these others.