Does your son not want to pass some on to his girlfriends?
About the charity thing, I don't think they are that fussy - from time to time we get asked by the school to fill a shoe box. You choose boy or girl and age band then fill it with useful and fun stuff - e.g. things for school toothbrush, gloves or t-shirt (depending on where they are going, small toys, crayons etc. I have usually manages to get the boys to part with something that belongs to them e.g. a car as well as buying things. I don't really know how they are organised, but I don't think they would be averse to used things (if you put the toys in a plastic bag in the freezer for a while after washing and drying, it kills of any remaining germs or dust mites)
re the freecycle thing mentioned by yummymum, here is a link to the page where you can see if there is a group in your area - I have used it from time to time to get rid of unwanted things e.g. a bed, they seem to cover everything.
http://freecycle.org/display.php?region=United %20Kingdom