The earlier the babies are handled, the better chance at being social. They need human interaction, and the more they are handled, the better they will be. It's okay to leave them alone for the most part the first day or so, but there's no harm in handling them from birth, if mama allows.
If mom is going nuts - and who wouldn't with 17 - and the babies are otherwise being cared for (milk bands), there is no reason to to let her out for 10-15 minutes, maybe a few times a day. Only if she wants out... Read her signals. I had one mom that wanted out-time from day one. I've had others that didn't. It's up to them... If they need a break, then there's no harm. Just be careful when attempting to touch the babies with mom around, until you know how she reacts.
With such a large litter, she may scatter/split the babies. This is normal, so don't worry... she's breaking up the babies into groups to feed. I would only supplement if mom is having problems, any babies aren't feeding (no milk bands). However, preparing in advance won't hurt, but many rat moms have done fine with large litters. Make sure to keep her milk supply up with things like eggs, soy milk, baby cereal, bits of chicken, chickpeas, blocks, etc. Make sure she always has plenty of water.
As a side note to Julia:
I've never had a litter that large in my care...
I thought you just had one litter, a hairless litter? Or maybe I'm getting confused. :?: