My point is, I am fully supported, and my job is to run our household(s).
Same as OP.
It's a very important role, and my DP massively appreciates what I do holding the whole lot together. He openly says he's amazed at what I do, and he couldn't do it.
When you have a child at school for 6hrs+ a day, and don't work, you kind of have to ask the question, what exactly are you doing dear?
She has time to volunteer (at what we don't know yet). He has time to play golf. Good for both of them. Her role in running the house is equally important as his role at work. She also hasn't indicated at all that it's because they need the extra cash. If they did, presumably she wouldn't just be volunteering somewhere now.
So, you can sort of conclude, as she says that this is now as DS will be at school, she's got extra time on her hands, looking to broaden her horizons, get back to some work, and I fully agree with that. So stop the volunteer work. Why should he sacrifice his time and take on what has been her responsibility, when she can just substitute the volunteer work for a paid job. "Oh but why should she????" Er...equally, why should he? Otherwise she's voluntarily reducing her time to run the house and shifting it to him. It's unfair.