Of course, your son will be disappointed. It doesn't make much sense to me either that it's age and height. Seems it would be more height, from a safety standpoint. I think all (well, most) parents can relate that it'll be tough to keep a 3 year old off the coolest looking slide, while his sister can go. Especially if he is use to waterslides etc.
You know the other day I made an tongue in cheek reply to a post and was accused of being arrogant and having a victim mentality. It was extremely surprising and hurtful to me as my comment was really taken the wrong way. I apoligized to the poster I was responding to (who was NOT the poster who judged me)- really horrified if I came off offensive. The OP sent me a very nice pm and hadn't been offended at all!
I guess what I'm saying is, I was shocked at the response you got from someone who doesn't know you. You certainly did not come off as "pissy" to me or looking for something to complain about. It's too bad, comments like this have to be made.
Thankfully, most posters on these boards, are upbeat, wonderful people. That's it! I just wanted to say, that I completely understood your feelings and felt offended for you to be responded to in that way.
Have a great, great, trip!
Jenn