Mate i feel for you, how can people be so stupid.
In terms of where you park, you can obviously never be that safe, I have a kid and im damn sure that I dont let her do anything stupid with the door, and I take equal care. Just because someone has child seats doesn't mean they dont give a shit....although i agree it increases your chances.
I always try and park in the parent and child places as although you may get a range rover next to you, the spaces are pretty big.
Hope you sort it out for a decent price.