My dd was fine on her Yr 6 trip in 2010 but went to a guide camp this summer and had to be picked up early after a couple of days. She is fine during the day when they're active but at night seems to develop the tummy ache (she is also extremely paranoid about being sick - though she never really has had much experience of it).
We also suffer at sleepovers and if she has her phone I normally get texts about how sick she feels.. So i'm never really relaxed when she's away as I keep thinking I'm going to get a call.
It seems as though the desire to take part in these things is overtaken by the anxiety.
I am a little worried about a ski trip she's going on in Feb and need to give her some coping mechanisms...