Wow, I'm shocked by some of the harsh replies.
I've no experience of parenting of children those ages my dd is only a baby. But I was that child who was up late, and honestly it's not fun. I remember being tired and asking to go home, I remember I couldn't really sleep in the next morning so was tired and it did have a knock on effect of me being tired on Monday mornings when I was going back to school.
So I don't think the OP is controlling for wanting a 6 and 8 year old in a reasonable time (what's average for these ages bedtime?) I myself think a good bedtime routine is important and that will stay the same at weekends, unless we have a big occasional event, weddings etc.
She wasn't saying they can't go out or anything, if they finished school at 3.30 they had 4 hours, more than long enough for a trip to the park and something to eat surely!
It sounds to me, that he struggles with the children OP. He's saying himself they didn't listen to him, he can't deal if they start playing up and then when your son is trying to speak he's pushing him. Is he avoiding being home with them to avoid parenting perhaps?
How is he in general at parenting, not the fun bits, but homework, reading books, bathtime, mealtimes etc?
If it's not just a one off, I'd be asking him to look into a parenting course.
Also, I think the fact you posted at all, probably says you felt there was something in the push and I don't think you should ignore that. I'd be very annoyed and for me personally it may well end the relationship.