AITA for telling my kids not to talk to someone?

I (27F) was babysitting 3 young children, aged 7-11. These are not actually "my" kids, but I am essentially their aunt. I took them to an indoor trampoline park for the afternoon and was constantly on the move to make sure I could keep eyes on them. There was a lot of people running/jumping around and I was afraid that if I took my eyes off them for even a second, something bad could happen.

So I noticed an individual with short stature (maybe a person with dwarfism?) was kind of following around/playing with 2 of the three kids I was watching. I believe he was older (maybe 20 ish) but he was shorter than my 9 and 11 year old. I kept an eye on them and I noticed he was following my kids around the trampoline park and being friendly. He was talking to them and they would respond but they were also kind of in their own world.

Eventually he had come over to me and said "your nephews are really well-mannered. They're nice. How are you related to them? Are you related to their mom or dad? Your more active than their normal babysitter. I'm sure you're getting your steps in following them!" On one hand, I don't look anything like the kids so I could see the confusion. On another hand, it felt a bit intrusive? He didn't tell me his name or anything. I was polite in my response but a little vague just because I was confused/flustered.

I didn't say anything to the kids until we took a water break. I asked the kids if they knew who that individual was and they said they'd seen him at another trampoline park they frequent but they didn't know his name. He had asked them who they were there with, who I was in relation to them (he came up to me after he chatted with them I think), and what our plans were. They seemed to be polite and friendly but not too engaged so I don't think the kids thought anything of it. I told them that they should just beware of strangers and not share any personal information (their phone numbers or where they live). They asked why and I said "Well you know, strangers can be dangerous and you never know about if people are good or bad apples."

Turns out that the individual was standing behind me and he looked really sad/hurt when he overheard what I was saying. I think he was going to ask my kids to play again but he turned away and went to a group of other people that looked like they were 18+.

AITAH? I didn't mean to hurt that guy's feelings. But in that situation, I was the only with 3 small children that aren't even mine and I would never want anything to happen to them while under my supervision. On one hand, I think it's really weird of an adult to want to play with little kids and follow them around. On the other hand, I can assume that playing in a trampoline park with people your size is more fun than with a bunch of individuals that are 2-3x your size.