I gave up teaching (Secondary - English) 7 years ago and don't regret it EVER.
When I first did the job I loved it totally and was very good at it. I worked every evening for hours after school and was very creative.
When I had my dd I went part time (2 days a week) which I thought would be manageable.
My dd was the first in nursery in the morning and the last picked up at night. She was so exhausted she would fall asleep face first in her supper.
Once she was tucked up in bed I would work til 11pm again.
I was under pressure to do more extra curricular activities (the same as full time staff and the same as I had done previously) on a part time wage.
I had the same problems as you mention with in-service training and courses. I was even sent on overnight courses and asked to share my knowledge with the rest of the dept, which on a 2 day a week wage was totally unfair IMO.
I had to clearly plan what I was responsible for and what the people who took the same classes as me were responsible for. My Dept Head had a copy of this but still shouted at me about what wasn't done by the people who were in the days I wasn't and who I never saw. She did this infront of most of the staff in the staffroom which was humiliating, even though they had known me for years and she was new and they knew she was wrong. She did apologise but in private.
During my pregnancy with ds my doctor (whose kids I had taught) became increasingly annoyed about he pressure they were putting me under and signed me off.
Staff then appeared at my door with marking for me as I was not at work!! 
All of that, coupled with the tiny salary I would earn once I had paid for child care, plus my dh's slightly increased salary over that time meant enough was enough and after my maternity leave was complete I handed in my notice.
I have never looked back.
I am SOOOOO much happier now, I have more to give to my children on a daily basis emotionally and physically and they are less tired themselves. It has been a brilliant decision for me and my family.
We have less money for luxuries but we get by and dh's salary has increased a little each year making it a bit more manageable. I obviously no longer have child care costs either.
For me the benefits of the holidays didn't outweigh the misery of term time and half the holidays were spent working or feeling guilty because I wasn't working anyway.
Good luck with your decision.
FWIW teaching is not the only job which will accommodate the holidays for the same (pathetic given the hours worked) wage and many of those jobs finish the minute you walk out the door - guilt free.