To be completely honest, I find the whole idea insulting. Yes, I have girly bits - this does not mean I chose Vet Med because I love all the little fuzzy wuzzy things so much and can't wait to share them with my own horde of offspring. I'm 26, married, and have NO intention of having children. I'm non-trad, I got my undergrad, started a master's program, and then decided to change everything. If I get in this cycle, I'll graduate the summer before I turn 31. I'm not spending this much time working for this career so that I can put it on a shelf and say "Look I have letters behind my name! Let's have babies!!!"
I know what I'm trying to say is not really coming across well. I'm not trying to say that women who go into vet med and want to have families are bad people (because I'm not!). However, I do find it annoying that mothers (in general) assume that the rest of us totally want to work extra, or late, or come in early so they can pick up child X, or take child Y to the Doctor, or any other shenanigans. Yes, I chose (choose) to be childless - this does not mean I want to pick up the slack because someone else chose to have children -because the fact of the matter is, children demand one's time.
I've never been a fan of the whole "mommy track" thing. It frustrates me that my husband can't take time off during spring break, or Thanksgiving, or Christmas... Why? because all the Pharmacists with kids have to take off so they can keep their kids who are on vacation from school. It is the same reason why I am never able to leave work early (for a doctor's appointment, class review session, etc.) - the other Technician I work with has children and has to leave by 4 so she can me home shortly after they get off the bus.
So, I guess, what I'm trying to say is - if you want to be a DVM and have children - kudos to you. Just remember that every time you take off early to pick up a kid or rearrange the day to take your child to the doctor...you're screwing with other people's schedules too. Your tech, who may have a class, or a dinner date, now has to work late unexpectedly. Or, if you close for the day because you have a sick child - your hourly employees are losing hours, do this too often, and you may lose good employees who must work to make ends meet. If you work in a multi-doctor practice, one of your colleagues has to stick around to make sure things are covered. Be grateful when people agree to help you - but don't exploit their kindness.
I don't think anyone assumes that another person wants to work harder in order to give a parent more flexibility. The parent obviously should try to work in a place that is friendly to this sort of flexibility. Obviously, you should probably avoid those places.
I don't expect other people to bend over backwards for me, but I do expect respect and understanding, even from those who do not have children. I know this is going to come across wrong, but from the sounds of your post, without any additional information about you, it almost sounds like you have a vendetta against parents. Maybe you've had some really bad experiences with parents who did expect the whole world to bend over backwards for them? I don't know.
A well-prepared working parent always has a plan and a backup plan. So when a doctor appointment is scheduled for one of your children, you know that you either already have that time off or that there is someone else who has already agreed to cover for you. There will certainly be emergencies...they always come up with kids. Your child breaks a bone on the playground at school...your baby at daycare spikes a scary-high fever...the school calls and says Johnny is throwing up and all three other people you have given the school permission to allow them to pick him up are unable to do so at that time...your babysitter locked herself and the children out of the house, or they got into a car accident on the way to practice...there is a whole slew of emergency situations that could occur. And, I believe, it's only respectful of other people to understand that the parent doesn't choose for these to happen, nor do they want them to. Not only is it inconvenient, but it is a potentially really bad situation, and the parent has to leave work, thus losing out on income.
Of course, I'm all about flexibility, LOL. Being a Marine wife means I live the motto "Semper Gumby". So when plans are changed last minute, I just roll with it. It might be stressful, and I don't always make the change in good spirits...but I do it because it must be done. I let that rule my life, whether at home or at work. Obviously, there are some things that I just can't do and that's that. But, in general, you just deal with it.
I'd like to point out that your husband not being able to get time off over spring break is no different from any other time or any other field. In some places, people can't get time off around the holidays because they have less seniority than their co-workers. Or maybe a person can't take time off in late summer because others who have been working there longer than them or who are higher on the ladder always take vacations during that time. Of course, on the other side of things, those same parents can't really take their vacation while their kids are going to school. I mean, I guess they could...there are parents out there who take their kids out of school for a week of family vacation, but it's really not ideal.
There are always two sides to a coin.
And other side of the 'don't exploit their kindness' coin is that if you feel like you are being taken advantage of, you need to speak up and say something respectfully and professionally. If you don't say anything, they may never know that you feel this way.