Okay, you have 2 options. The first is to use the existing consent form, filling the blanks as follows:
I Parent of Kasuni grant permission for Kasuni to act as guardian for Kasuni during the convention. (you can scribble out the "over 18" portion, to make it all honest and such)
Alternately, you can have your parent write out a consent form which absolves Kumoricon and its constituents, and puts you into your own care (we aren't exactly fascist about it being -our- form, as long as we have one that will cover our rear in case of bad things).
In either case, if we are given that, you should be able to get in, as all the legal aspects will have been handled.
PezCat