I understand how disappointing it is for children who aren't tall enough to ride some of the rides, but I'd like to remind parents that those restrictions are there for a reason. I used to work in an amusement park (not WDW ~ the place I worked is closed now...but not for this reason...management didn't want to spend the money to improve it so that younger people would want to go), and we had an incident where a parent somehow got a child who had been deemed "too short" at the entrance onto the ride. I was working at a snack cart at the entrance and saw that in spite of everything, the child was a good inch to inch and a half too short for the ride and the ride operator explained to the parents that the height restriction was for the child's safety ~ the restraints weren't guaranteed to keep anyone under the height restriction safely in the seat. The parents said that they would have the child wait at the exit and got in line. Apparently the ride operator at the seating portion didn't get the radio message to check and make sure this child was measured again there, and the child's parents put her on the ride ~ it was a raft ride. Well, towards the end, the child slid out of the restraint because it didn't fit her properly. Thankfully she went into the boat and was not injured. There was a pending lawsuit, but as soon as the family's lawyer heard our deposition (yes, because I had been present at the scene of the original measurement I had to give a deopsition) of what happened and that it was verified by no fewer than 4 people talking separately, the suit was dropped.
I don't have children, so I can't say that I fully understand how your heart breaks when a child is not allowed to ride, but I would encourage you to think about what if your child was under the height restriction but because of shoes or whatever was allowed to ride and something happened. It could be worth encouraging the child to wait another year or so (and I understand that for most of us WDW vacations are not annual things) for their own safety and your own piece of mind. I'm not trying to be inflamatory, just to present another side and the reasons for the height restrictions.
Thanks for listening.
~Beth