Lexi and other kids

I am not all that concerned about germs - but maybe I should be! We have had two incidents in the last couple of days where Lexi has ben interacting with other kids - and I am wondering about their germs. On Sunday, the little African girls at church wanted to touch Lexi. I can understand that. So they were holding her hands and touching her face a little. One of them also promptly picked up Lexi's pacifier which is attached to her clothes on a plastic chain and stuck the tip of it in her mouth - the girl's mouth, not Lexi's. What to do? I wiped it off on her bib. Is that hygenic enough? I don't know. And what to say to these girls? I don't even know if they speak English - it might only be Kiswahili. Then at the Christmas Eve service, a little blond girl wanted to play with Lexi as if she was a doll. She was gripping Lexi's arm rather firmly - but then Lexi grapped the girl's curly hair. So maybe they were even. But the dilema for Stephen and I is - what do we say to these other kids that are interested in our kid? At what point do you tell them 'no'?