Aw, congrats on the new litter! Glad to hear everything went well for Fifi and her babies!
I kept the food and water (and litter box) close to the nest and momma kitty (Shenzi) would get up every now and again to eat, but really not too much the first day or so. Mainly, I think they are pretty worn out from labor and delivery. Trust me, she will make up for not eating too much the first day eventually! Especially because of all of the little ones who are feeding off of her. As long as you keep her essential items pretty close to the nest, she will be comfortable leaving them to eat and use the litter box.
I did notice, after a few days, Shenzi would come out of the nest, after the kittens fed and were settled in, just to lay down for a rest and for affection from me. She would go back after a little while or if they started crying, but I think she needed a break every now and again.
I handled our kittens from the time they were born (no gloves or cloth, just clean hands)...mostly to weigh and inspect them, at first. I always approached the nest and would talk to the momma kitty for a while, petting her and then petting the kittens. She never had a problem with my interacting with her kittens. The only time she would get concerned was when the kittens would cry, then she would get up to investigate. She never showed any aggression or anything, just concern. I remember one time when I was weighing our little 'screamer' ('Rabbit', the vocal little one), he was crying and Shenzi came out of the nest and took him right off of the scale and returned him to the nest...it was so funny.
I would take your cues from her, does she mind your being around? Does she act aggressive or defensive when you are near the kittens? If not, I am sure she will be fine with your handling them a little bit.
Good luck with your litttle fur family!