S.W.
Hi C.!
How lucky for you that God has blessed you with a sweet little boy!
I am a mother of two, a 7 year old and a 3.5 year old.
I don't know if it will help - but when i trained my 3.5 year old boy, he did the same thing - he wouldn't pee in the potty - until i tried something - i encouraged my hubby to take him with him EVERY TIME he peed (at home; at a football game; at a restaraunt) and then he saw "daddy" peeing - and once he learned that he was allowed to stand up to pee (they are tall enough - they may need to stay on their tip toes - but they are less accurate when standing on a bench) then he would pee on the potty - but only standing up - once i let him stand up to pee we were out of pull ups within days - literally days. I dont' know if it will work for you - but it may be worth a try - plus the other up side to that is you dont' have "retrain" them later when they are older and wwant to stand up!
Good Luck!
S. W