I don't allow full day visits. They may come twice for an hour each time - one is just to play while mom and I sort of talk about the kids, the group, expectations. The other visit I will let them play for a bit and then do a small circletime or activity if I think it will go ok. What you are dealing with is a mom with anxiety issues and that is going to rub off onto the children. Expect her to be uncomfortable with leaving the children at least for the first while. Visiting with you at playgroup would be a good first start because you will be able to see if she can even separate from her kids there so they can interact with peers and so can she. You will learn a lot.