MKB party #3...4 years old!

We did it again. This year we totaled about 125 people- give or take a toddler or two. We're all in a bit of shock that Makena, Keller and Bradley are 4. What's even more shocking (to me!) is that both Keller and Bradley have added second brothers (meaning a third boy to each family) in the last two months. Don't ask. The answer is no :)
Back to the subject at hand...we upped the ante this year and had two water slides- the giant orange one we had last year and a smaller one. The kids, obviously, have all aged another year so almost all of the ones who were timid with the big slide last year conquered it with no problem this year. The line to get up the big slide was nose-to-rear the entire time and we had a constant problem with kids wanting to congregate at the top of the slide. We'd look over and notice that the six kids piled on top of each other at the top were causing the slide to start sinking. Is this a forebearer to public loitering?
(I realize I'm struggling with under and over exposures here- I'm not good enough to adjust on the fly and play partial party hostess)
Can you believe they're this big?