Mine separated when I was 20 and at uni. I relate to what Wigeon was saying, that it was less the split that was upsetting than how it was handled.
Bad:
Mum told me and my older brother about six months before she left that she was seeing someone else, but didn't tell my younger brother (he was about 16). So both of the older sibs had to shoulder the dilemma of which parent we stitch up by either saying something or not saying something. And younger sib had to come to terms with having been 'excluded'. Not nice.
Better:
Mum comes clean to everyone at once.
Bad:
Mum abruptly announces she is leaving, puts some things in the car and buggers off while older sibs are both away travelling. Younger brother is left as sole caretaker of a sobbing incapacitated drunk.
Better:
Mum confonts the issue (she's unhappy and has been for years, Dad is an alcoholic, she has met someone else and is leaving with him) to everyone, we cope with the shock and pull together as a team.
Personally I wish she had left sooner. I grew up with unhappy parents, one of whom would regularly drink a bottle of Scotch a night and fall snoring onto the kitchen floor. I believed for a long time that my conditioning was irreversible and that no matter what I did I'd never be able to have a happy relationship myself.
It took me ten years and a lot of therapy to get to the point where I could have faith that I'd not just end up in the same predicament, and hence stopped avoiding relationships and allowed myself to be open to love and thinking about long-term commitments myself.
As a footnote, both my parents are now remarried. Dad no longer drinks. Stepmother can be a PITA, as she seems very threatened by Dad's children and has thrown some hardcore tantrums in the past. But on the whole everyone is now much, much happier. IMO the bottom line is that divorce with children involved is a big shit sandwich, and everyone has to take a bite. It's going to be like that whether you do it sooner or later.
Each situation is different though. You sound as though you are really trying to work out what's for the best. Good luck in making your decision.