Seaside - I think this is just a boy issue, my son always managed to miss the toilet when he was a little un, I put a ping pong ball in the toilet and this solved it, he'd aim for the ball, fun for him, no clean up for me but your son is a little old for that. Little boys are just dopey and they're not the ones who have to do the clean up so there's no incentive for them to aim. Tell him if he can't pee in the toilet he's going to have to get down on his hands and knees with a scrubbing brush every day to clean the mess he made
I do think it's healthy for a mother to be able to talk about her son's penis with him in a strictly straightforward factual way, there's being open with your sons and being sexual with them and sometimes people are unable to see the difference. Keep talking, keep the channels of communication open then if there's a problem they're always going to be able to come to you for help.