M.D.
So last summer I took my 3 kids (11 year old girl, 9 year old boy, 7 year old boy) to Busch Gardens several times without my husband. I had to use the restroom each time we went and the boys came with me. I was NOT leaving them outside to wait by themselves in a crowded amusement park.
We used the family restrooms when available, but if they weren't, the boys came with me. Not one person looked at me strange, and all of my kids look older than they are.
At local places, I give all of them 2 minutes before I'm busting in the door. It took me going in once on each of them to know I wasn't playing. Sorry, but their safety trumps anyone else's opinion, in my opinion.