D.S.
It can get frustrating huh? My husband has been deployed twice as well as numerous other schools & such that have kept us apart so with that said here is my input - hope it helps some :-)
Why do your plans have to be put on hold if he takes this class? If your 8 year old is in school & your 3 year old is in daycare 3 D. then go to the Y during those times. Most Y's have childwatch also so take advantage of that. Walk with your kiddos, bicycle together, chase them around - it can be so hard to get motivated, sometimes I am extremely demotivated myself! As far as school goes, if you are attending online then you can usually structure your school time around when the kids are away or asleep. It's hard - I know, I'm currently finishing my degree online as well & am up at about 4 every morning to get in the time needed to do it.
Find it in yourself to stop overdoing it with the friends & neighbors - still be kind & considerate but if asked to go above & beyond just let them know that right now you need to take a season to get yourself back into shape. I'm all for helping other's when I can and sometimes even when I "can't" but if you find that you are draining yourself to the point of not being able to maintain your family & your health then it''s time to step back & refocus.
My schedule is pretty nutso & sometimes seems chaotic, my husband is in training right now (EOD - military) so he is out the door by 4:30 every a.m. and usually doesn't get home until around 6:30, I am in school full time, we have 3 kids & we homeschool so I'm learning new ways all the time to do things more efficiently & get in the excercise that I need (MUST SHED the extra weight from the recent baby!). If I can be of any help just message me :-) it will get better!! Mucho blessings.