If you are worried about urinary calculi get a hay sample (chop up a ziplock bag of hay into tiny little short pieces and mail with form and a small payment via check) and send it in to get analysed. You're looking for a calcium to phosphorus ratio between 2 to 1 and 4 to 1. That will keep them safest. Giving cookies once or twice daily should not give your boys stones. Loading them with unbalanced grain might.
My analysis(es) that I've run show me that my orchard hay tends to always run a little high on phosphorus which can cause stones all by itself SO I give alfalfa pellets in addition to hay (and right now I mix in a little beet pulp and balanced goat grain because I'm growing out two lamancha bucks that need it).
But that's just what I do.