stood up...what would you do?

I offer no-cost sessions, so as to not limit my clientele.  I genuinely want to be a photographer that makes photo shoots worth my time away from Jonas but also want "ordinary" people to afford professional photographs.  Is that too much to ask?  I go to shoots on faith that clients will show up and will order pictures.  Sometimes clients don't order enough to cover a babysitter, or not enough to be worth setting up my backdrops.  Very rarely this occurs.  I've even had one family not buy anything at all.  I personally think that is very rude.

The point of this post was to vent a little and also ask some advice...
This weekend I was referred by a mutual friend to a couple who wanted beach pictures.  I live in Savannah now, so a one hour drive gets us to the beautiful ocean.  I was to go yard sale-ing that morning but since I booked a shoot, I cancelled that and afternoon swimming with friends.  My husband had to give up his Saturday plans as well, so that he could watch little Jo-Bro.  No big deal, right.  Well, we drive all the way to Tybee (one hour each way, plus $$ to park).  They didn't show up.  It is four days later and they have not called me back.  So what would you do?  I don't normally charge session fees, but that was an expensive day for nothing.

Deep down I want to send them a bill for gas/time.  I was thinking at least $50.  Seriously.  I have since decided to revamp my pricing.  I still want to be affordable for anyone, so my philosophy now is to charge a $75 sitting fee, and once your shoot is over, you will get a $$ credit for prints.  I was thinking $50 of the sitting fee would be "refunded" toward photo purchases.  It basically guarantees a $25 sitting fee and $50 worth of photo orders.  Unreasonable?  I think it is pretty cheap!  This is mainly for on-location shoots where limited travel is involved. 

I have to keep my prices competetive with the mall/instant print labs out there, but I offer much better pictures on location, so there will obviously be a higher cost.  I am getting tired of "giving my work and time away" so I need some feedback.  What would you do?

1.  Should I bill those clients who stood me up?  How much?
2.  Should I insist on a deposit for photoshoots?  Is $75 too much (even with getting $50 credit)?
3.  Would it be better to charge by the mile?
4.  Is it best to just create different prices for different type photoshoots?  (baby, maternity, beach, etc - each getting their own sitting fee more tailored to what is involved)
5.  Is it bad to start charging sitting fees after not for so long?

I feel like the past 6 months of business were a learning experience and now that I've invested so much in equipment and such, and improved my skill level, does that warrant a change in rates?

Your input is appreciated! :D