Mine are 19, 17, and 10. I'm in my late 40s. Until nursing school I was a work-at-home SAHM, doing medical transcription and tutoring--so I was nearly always home, very available, ready to do things at the drop of a hat, and available as a chauffeur, coach, etc. My husband has always worked long and irregular hours and been only minimally involved in the kids' lives.
The older ones have finally sorted out that I am, indeed, a full time student. I did get the "aren't you a nurse already?" line from them after taking one prerequisite! If only it were that easy! They now do seem to understand that I'm gone pretty much four days a week.
At times they resent school--like when I'm not available to chauffeur (or lend my car) to the 17 year old. My 19 year old is home for a long weekend (college freshman) and asked me to go to a movie with him last night--I had to say, "Sorry, I have a test tomorrow." I really would have liked to go with him--but I just couldn't, I had to study and get my rest.
The little one takes it the hardest. Sometimes she tells me she hates me, or leaves me notes saying she does. I'm just not available the way I used to be, and she tells me she doesn't like it. We always spent a lot of time together and had fun together. I am home all but one afternoon when she gets off the school bus (and the 17-yo is there then), but I need to study or I'm typing up care plans
on the computer. Often, she comes with me to study at the library or at a coffee shop, and then I take her out for ice cream after.
Her father has had to pitch in to help with her--driving her to ballet class, being home for her on delayed opening mornings, etc--and he does not do so with a smile on his face--so that adds to her discontent. I try to carve out time for her daily, but it just isn't the same. She really is a good kid and is adjusting, but it is hard on her.
My older ones are awesome kids--never cause any trouble, never in trouble, moral, good students--and at times I worry that if #3 turns out to be a more troubled adolescent, I'll feel very guilty for not being there for her because of school. I've enlisted the older ones to pay more attention to her, and they do. I like to think I've laid the right foundations for her, and that she's learning to be more independent--but you still worry what the effects of your actions are on them.
I've applied for an externship for the summer, but, because I want to be around for her and the rest of my family, I've asked for only 24h/week--they've said they may give the slot to someone who's available full time. If so, then so be it. I'm just not ready to give up the entire summer and not spend a good chunk of it with my family.
So, anyway, my kids are great--but it has been an adjustment and the kids are often annoyed that I'm not as available as I used to be. Nonetheless, they're supportive, and I think they'll turn out fine. I, too, really felt I had to wait until they were these ages to do this. Nursing school is a big strain on my marriage--my husband would rather work 18h/day than have to tend to his kids, but this has been a struggle with him for the last 19 years--so it isn't news---I knew going in that he wouldn't be all that supportive and that the kids and I would have to endure his ill humor over increased parenting responsibilities.
Best of luck to you as you sort all this out. Feel free to PM if you ever need to vent!