WABU to 'volunteer' him for this?

[Dieu]

Good morning everyone :o)
I'm having one of those 'is it just me?' moments, so I'd appreciate your thoughts on whether or not I have been unreasonable.
My husband (we're separated) came round this morning to take the kids to school. He has the dentist anyway this morning, which is directly behind their school. This is why he offered to take the kids to school this morning. A rare treat for me to miss the am school run (by bus, as I don't drive)!
I usually help out in my 7 year old's class on a Wednesday morning. This is nothing that's set in stone, it is absolutely not a concrete arrangement, rather an opportunity for parents to get involved in the school, if they so wish. I tend to do it every Wednesday morning anyway, and really enjoy being with the kids. Anyway, I had some stuff to do around the house this morning, and it was just too good an opportunity to miss being able to stay home!
I asked M. in conversation what time his dentist appointment was. 9.45, he said. Ooh, said I, perhaps you could go into the classroom instead of me this morning? The helping out, usually with a set task, only takes about 20 - 25 minutes and school starts at 9.
Cue lots of huffing and puffing from him. He didn't know where the classroom was. Being with the kids wasn't his 'skills set'. He didn't have enough money on him for the parking for that length of time (I gave him the extra money). I never think about the practicalities of these things, apparently. And many other passive aggressive comments muttered under his breath. I should add that he is a high earner in a very responsible job. Not some numpty.
So the upshot is that he will do it, but only after making me feel like shit about suggesting it :o(
Funny, but I was chatting to a friend last night about sponsorships for the kids' Sport Relief activities. She mentioned that her husband had taken their forms into his work and ended up getting their kids loads of sponsorship money. I was stunned. It never would have occurred to me to ask M. to do this, as I would have been faced with the usual fuss like I've outlined above. It's unnecessary and exhausting.
Maybe he thinks it's 'women's work' to do this kind of thing. I don't know. Sigh Would like to hear what you think. Thanks in advance for reading.

[Dieu]

Yup, I was unreasonable, as acknowledged earlier. Got it!