Don't worry about her. Buy the kids beds. Know you are doing everything right, and keep doing the right things.
Worry about the things you can control, be aware of the things you can't.
Know that when you are requesting and negotiating, that you are comfortable that your home, is your kids home.
In regards to flight time, 1.5 hours is nothing. But is there other travel time included. ie, hour to the airport, etc etc.
Be aware of yourself, your children, and their mother. 2 weekends per school term, is not much time, but probably reasonable if travel too far. Can you guys go to them? 2 weekends per school term they come to you, and you go to them, and have day visits 2 weekends per school term. The more you base your life around your children, the more content everybody is.
If the mother works though, and the kids are home by themselves at 12, maybe you should be requesting the mother gets 2 weekends per school term and half the holidays, and you guys get custody.