Ok, boy or girl.. here are a few ideas...
I had to do this for acting class, it was a improv class, and improv lesson for stage makeup.. (sort of like how would you make one look old quick)
We would put baby powder in the hair.. yes there are fumes or puffy clouds, so be careful.. some just shook it in the hair, and some put it on a brush and brushed it on with semi wet hair
ok, you can put age lines near eyelids with eyeliner, and cheeks/chin.
You can put hair up in a bun, or just older clothes... no cane, use a broom handle, or a big stick (call it a whittling stick or a walking stick)
Maybe some old eyeglasses if you have some old perscriptions/frames floating around the house.. you can just pop out the lenses.
NO older clothes.. if he has dress pants he can call them trousers or dungarees... and a button down plaid shirt buttoned all the way to the top, with black socks, and loafers...