DD2 age 10 went on her first ever sleep over last night 
She has been with us over 7 years, but we have no family nearby so she's never stayed at grandparents etc. without us. She's always been quite clingy and doesn't like goodbyes. We arranged it as she has a school residential in the spring so we needed to know she could do it.
Sounds like it went well, though she had trouble settling at night. However the other Mum has known DD2 almost as long as we have, and looked after her really well. Tonight she has needed some extra hugs but is OK.
I survived too
, and now feel a whole lot more confident about the residential (which we had already paid for).
It wasn't so bad with DD1, as she had her first residential with us while still LA, but she was still sort of used to moving around, so took it in her stride (and it wasn't a boat ride away either!).