Which is more important?
Your son getting enough sleep or keeping him awake until late one time a night and him getting overtired and then it affecting his quality of sleep and him being tired/fussy the next day???
It takes at least a day, for a child to catch up on sleep. And lack of sleep affects a young child the next day.
My vote is:
having your Husband put him to bed at a normal hour as is his usual bedtime.
And when you come home, do not wake him up.
And remember, after you come home at night and if your son is still awake, its not like he will be going to bed RIGHT then as soon as you come home and walk in the door. He will probably want to stay up and refuse to go to bed right then... and he will want to play with you and you will too. Thus, his actual bedtime and falling asleep time on those nights... will be MUCH later, than just a 1/2 hour.