Wow Sara I hope they dont just turn up whenever they want and stay for a few nights / ask for a feed!

Perhaps let them know that it would be appropriate to visit for the hour e.g. 3-4 on thursday, and thats it?

Then they know

A - they cant stay with you
B - you arent feeding them / cooking with a newborn
C - they cant come whenever they want!

I reckon get it all over and done with in one shot!