What a great night at King's Island. My numbers could be off, but the crowd for Friday night looked like 5,000 and Saturday night looked like 25,000 in the park.  Wait times on Friday was not bad.  20 mins was the longest I waited for a ride and Flight of Fear was a walk on. The mazes was another story. Field of screams was about an hour wait. 

Saturday was another ball game. It took a half an hour just to get in the park since the lines to get in was crazy long. Lines for The Beast was 20 mins in the beginning but jumped to 90 mins plus. Despite the crowd the mazes were great and the scareactors did a great job. Love them sliders!!!!!

I was not there Saturday, but there were way more than 5,000 on Friday night. My guess would be 20,000 or a little more on Friday night. Sounds like you might close to double that for Saturday by your description. Of course we will not know for sure and I am guesstimating myself. Having been there of a full capacity nights at haunt in the past I can sort of gauge.

Glad you have a good time!