Would you think they are Pedophiles?

Example 1: You have a younger sister (or a daughter), and they are about 4 years old playing at the park. A few teenage boys/middle aged men approach them and start to play with them. Would you be worried that they are some kind of pedophile?

Example 2: You have a younger brother (or a son), and they are about 4 years old playing at the park. A few teenage girls/middle aged women approach them and start to play with them. Would you be worried that they are some kind of pedophile?

1.- Yes, unless I know the boys
2.- Nope, I would just watch in case that something happens