They’re too young too have the amount of veggies that adult rabbits are given, but it’s okay to give them tiny bits of fruit or vegetable. There’s a list here on BinkyBunny of rabbit safe fruits and veggies. Other suggestions for treats could be papaya tablets, craisins, raisins, or other treats that are sold at trustworthy places like BB. Bits of carrot also make good treats as carrots are too sugary to feed all the time. Just be sure to only give a new food every couple days or so rather than a bunch of new foods at the same time to make sure that each new treat isn’t too hard on your bunnies’ tummies. 
Foods that are not safe to give to rabbits are yogurt drops (even though they’re sold as rabbit treats), any dairy, cookies, cereal, bread, crackers, anything with nuts or seeds (even though those are also sold as rabbit treats), ect. Basically most human foods besides fruits and veggies, they can cause G.I. Stasis.