The fact is, your ds is YOUR son. He is not THEIR son. You are his guardian, responsible for him, and everything that happens in his life should be run by you.

If you need your dh to understand, maybe try talking on his level - what if your parents started organising car services on his behalf, or just took his power tools out for the day to give him a break? Obviously, they're HIS, and they would need his permission, or to check with him first.

Perhaps fill your diary in with things. Even if you have a scheduled weekend to yourself, so that you can say, no sorry, we've already got plans for that weekend. Call it 'marriage time' or 'family time'. And then book in a weekend for them, say once a month (or whatever suits you), and then when they say hey let's do this, perhaps you can say well, not this weekend, but we'll see you in a fortnight!

Wishing you well, it's tricky ground to navigate hey.