I'd imagine it's something along the lines of the rules for taking animals to shows or sales - they can go and come back the same day, but it triggers the standstill again on your holding. I don't know exactly how to apply or who to ask, try environmental health, or have a mooch around on the eaml form?
What a lovely thing to be asked to do, got some new weaners this afternoon and they are just darlings, kids would love them! Hopefully you'll be able to do it without too much hassle, but how feasible would it be for them to visit you one day in future?