to answer your questions.
You are correct in assuming that ants need energy reserves to last during their diapause/ hibernation similar to a bear. Since they barely move, they don't need feeding either because they should have enough energy reserved. Ants have a biological clock built in telling them when colder month are approaching and you'll notice that they begin to forage less, and certain species will also have swollen gasters indicating they're saving food/energy for the winter.
to answer your second question, it can't hurt to give them a meal before hibernation, maybe their favorite sugar water and protein. They may not eat as much as they normally would, especially if they're full from already saving up food in their gasters.
good luck with hibernation!
Edited by KBant, November 22 2017 - 5:20 AM.