DS's 7th birthday trip-parents too?...

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DS 7, wants to take a few friends to local museum- it will involve short bus trip to get there. Would you expect the other parents to come? Would you want to come if you were parent? How long should we allow for the trip- parties are usually 2 hours long but realistically we'll need about 4 hours for a trip to museum inc travel to and from, is this too long? Help....

No, I would not expect other parents to come.
I'm not a parent so can't give a view on your second question.
4 hours I feel is fine, though you may need longer.

When you say a few friends, do you mean 2? Or are you talking more than that? I feel you need to be realistic in how many 6/7 year olds you can manage. Three children in total I feel is reasonable, two children would be easier.

I've nannied for families with 4 children and taken all 4 out on trips... they were of various ages though and knew me well. Keeping an eye on 4 children in a museum even when you know those children well can be tricky, as one child may want to see a particular thing while the others may not.

How well do you know the other children... do they come over to your home quite often on playdates?