L.,
Wow, that is really young to have a child potty trained. Especially a boy, since boys are not typically fully potty trained until they are three years old! Does your son indicate that he needs to use the toilet, or do you just know his scheduled well enough to know when to put him on the toilet? In response to his wanting to stand while peeing, I know some people who will give their son something to aim at so that it won't get everywhere, such as a cherio. But please don't force your child to toilet train before he is ready. Research shows that by forcing the child and repremanding etc.. can cause a lot of psychological damage. It is best to let the child do this when he is ready.
J.