unless there is a documented history of her not complying with
orders./agreements (e.g. she has been penalised by the court for breaching
orders), I think a court would be likelyto say that handing over the
passports when you collect the children for the holiday is reasonable,
unless you can show that you need them earlier (for instance, if you were
going somewhere which required them to have visas)
I don't think
it would be unreasonable to ask for them at the previous
contact (i.e. the last time
before the holiday) perhaps on the basis that you want to be able to get
copies done in case of loss or damage, but I don't think you'd be justified
in going to court on this issue alone.
Has she confirmed that
agreement in writing? If not I would suggest sriting to her (e-mail is
fine) saying that you just wish to let her havethe details ofthe booking,
and to confirn the agreement in terms of when you will collect the
children, that she will hand the passports over to you and that you agree
to return them to her on the children's return home, and also setting out
any other specific details you have agreed about the holiday.
Ask if you can please confirm that that is her understanding also, or let
you know of anything you've missed out. That should give you some peace of
mind and makes it harder for her to subsequently change her mind