Once you start looking you can find many grain free, all natural, even organic treats. Just be sure to check for recalls regularly on whatever food and treats you are feeding your dogs. This can be done easily by googling the product and the word 'recall'.
I like to make my dogs treats at home! We dehydrate sweet potato chips in the dehydrator, though you could bake them on a low temperature as well. There are also tons of grain free biscuit recipes you can find on Pinterest or through google. I like to make my own biscuits becasue then I know only human grade organic non-GMO ingredients are going into my dogs treats!
Store bought treats that are brands I trust (after doing extensive research) include: Whimzees Dental chews (the best dental chews on the market I think...a tip also, you can get them for half price on amazon!), Yummy Chummy soft grain free salmon treats, and Wet Nose Organic biscuits and bones (most are grain free).