to Purrs
Whats her name?
I dont think she will have any problems but this and the question as when are they due really is for your vet to answer and a phone call should bring you the answer.
I am pleased you have homes ready for the kittens and please note they really shouldnt leave their mumcat until at least 8 weeks old.
There are quite a few on here who can give you advice about what happens and when and what to do but will all be snoring their heads off probaly by now, so tomorrow you may get some better advice than I can give you.
Its so easy to forget everything at the vets even when not shocked
Try to make a list of your questions and that will help a bit, but nothing ever quite goes to plan.