It think it's great that he wants to work at 16! I know it will be sad for you, letting your son go and do his own thing! Sometimes as moms we have to just suck it up and let them be, and grow on their own, do things their way.
My brother and I had jobs when we were 14, and it made a HUGE difference in our maturity, and teh way we viewed life, and AND it made us appricate our parents more, and sooner tahn most teens did.
AND having been a teenage girl...It SUCKED dating a guy who didn't work! That meant I had to foot the bill, so It really impressed me and my parents when a guy had a job, and car, etc.
It looks awsome on a resume, it shows ambition.
I think you have a pretty wonderful son there, and have done a GREAT job raising him!!! Look what all your hard work has done...I sure hope when my boys get to be that age, that they will have the drive to want to work, and to be responsible and mature!
(I added more...)
ALSO, If you visit him with the twins, It could have a Positive effect on them! What a good example for them to witness, and strive to be like!