E.B.
With three kids and a "not much help" husband-I did very little volunteering at the schools. I usually took one job a year at each kid's school ( a bonus for me if there were two in the same school -but that hasn't happened for a while!) Room parent at our elementary was very simple-three parties a year and no other responsibilities. Personally I think volunteering has gotten so out of hand at some of the schools-it is almost as if the volunteers are looking for ways to spend their time there, rather than the original purpose of helping the school and teachers. I made sure I was room parent for each kid at least once. If I wasn't room parent then I volunteered for one function, one or two field trips, whatever-but I did not ever commit to a full time position every week. There are some people who love to do that and are very organized and can handle that; I am not one of them. After fourth grade, your kids would just as soon not see you at school anyway! The positive for you in volunteering at school parties is you meet other parents-a good way to get entrenched in a new area.
Fundraisers-ugh. If they have an opt out-I send a check and forget about it. I am quite big on not having all the extra junk around the house. Some fundraisers don't get done at all. O well. Frequently if they have a "don't buy anything, just send a check" opt-out option-the amount your kid needs is half of what a kid that sells stuff needs for the prizes. And the prizes are junk anyway so your child will recover if he didn't get one.
I guess what I'm saying is-you can't do it all and you don't need to try. Everyone is in the same boat. Other parents are feeling the same way - do what you can and forget the rest.
Just say no.