Although our's have had a change of personality in the past when they go into kennels (as in our usually fairly laid back silent lab is a barking excitable twit, with a very waggy tail) there is never a problem with eating for either of them. I tend to send their own food as I use a local brand, and they will feed whatever they need, whenever they need it. They tend to stock a wide range to suit all tastes. As for exercise, you will need to ask lots of questions to make sure it will suit your dogs. There is no way we would send our's to somewhere who only do lead or yard exercise. We have now found somewhere who exercise in packs in a large field, so that the dogs have stimulation and socialisation, get more than most as they only need two staff to exercise all(but the nowty ones) so they get a minimum of 90 minutes a day of play and interaction, split into two or three sessions depending on the weather. They come home well and relaxed and happy...and the lab is quiet there! Not the cheapest, but worth seeking out. Our's breed working labs.
As for notice, the good ones get booked up early,and I would be suspicious of any kennel who can take new dogs at short notice in busy periods.