Well, my kids are still little so if you are talking about with friends that hasn't happened yet, but my oldest was 21 months the first time he stayed at grandma's. I know that for sure because it was the night my second one was born!

I'm getting a little better about it now but I never wanted my kids to be away from me at all when they were littler.  Now if my in-laws ask to take one of them overnight, I gladly send them! :)  I don't think they did an overnight before age 4 though.

When you say over night trip are you including a sleepover at a friend's house? I have 5 kids so it is so varied. My littlest ones have never been on an overnight trip without us. My 3rd son was on sleep overs since 1st grade so was my second and they went with the school to a YMCA camp for 2 nights in 5th grade. For my daughter I was on that trip as a chaperone. She went on sleepovers starting in 3rd or 4th grade.

My oldest had her first real sleepover in first grade, but she was just across the street. Actually she kind of had a sleepover just before she was four at our next door neighbor's, but that was because I was in labor with her little sister so I don't count that! As far as going away someplace to spend the night, they've not done that. Neighborhood sleepovers are as far as we've gotten.

age 9...only stayed at his grandparents overnight before then. But, overnights don't seem to be real big with my son and his friends.

I let them start pretty young as long as there was a parent I could trust, I thought why not?

My kids haven't done too many sleepovers at friends, but at 11 they do go away for a two day camp with their school.  

My daughter was in Kindergarten. My oldest was like 4--the sleepover was with his best friend who lived right above us in the apartments...those two were inseparable

My kids were 4 when they had their first sleepover at their grandparent's house.