Baptism Invitation

Hi,
My daughter will be baptised in the UK (we currently live in NY). How can we ask our guests that monetary gifts would be best for our daughter. We are afraid that if we receive actual gifts we might not be able to bring them back home. I was also thinking of putting red envelops (we have an oriental background) with the invitations for the money.
Is this a good thing. I have already designed her invitation but stuck on this particular thing.
Many thanks