You may have to separate them to prevent the danios from constantly outmaneuvering him to food. I'd just cup the little suckers and let them sit out if they're going to be a problem for the betta. Well, really, I wouldn't keep them together to begin with, but that's just me.
It's entirely likely that your betta isn't interested in food the first day he comes home anyhow. Many of them couldn't care less about food after the jostling ride and new environment they've already been through, and they generally respond better after having a day or more to become acclimated. I've had some bettas that have refused food for over a week when first coming home from a store, but in time they will eventually get over it and get hungry enough to eat.