Anyway, like I said, no specific questions, but any general sort of advise or encouragement (especially the latter!) would be appreciated
Two days a week sounds about right for kindergarten-level homeschooling, and you might find that you get by with even less.
As for getting some decompression time for yourself, I would look for it in your partner, or a close friend, or a babysitter if you can afford that, rather than in more activities. Then you can leave the toddler as well and get a true break. I never was able to make nap time feel like a real break.
"Let me see you stripped down to the bone. Let me hear you speaking just for me."
I agree with SweetSilver. Two days is plenty, although you would probably be surprised about how much learning happens at home. I imagine that you want to use the unschooling center as a place for her to interact with others, since you mentioned that as a concern. Also, babysitters are much cheaper than private schools. Therefore, instead of budgeting for the expensive school, use a portion of that and dedicate it to "mom's break time"--it would include the sitter and some money for a coffee, lunch, pedicure, or whatever suits you. Hopefully you will meet some people that you both like at the unschooling center and you can have playdates or coffee dates.
Good luck, homeschooling can truly be wonderful! Not "every" day is wonderful, but the experience is. :-)
Consider finding a mother's helper also to help with the little ones so you can get uninterrupted homeschool time. My dh works off so during his week home I take some time away from the house alone to get my break. It can be done. Just remember to relax and have fun with it. Especially for K it shouldn't be too complicated so it won't overwhelm you or your children.
Michelle mom to DD , DS , & lil DD plus and spending my days