Hey there,
Since your buns are Nethies, I would say anywhere between an 1/8 cup-1/4 pellets a day although personally I think 1/4 may be on the high end for their body weight. I would suggest somewhere in the middle? My buns get a little less than 1/4 pellets a day and two big salads a day.
I also noticed you said something about making pellets a very small part of their diet? I know some buns can go without pellets altogether but you should really talk to a rabbit-savvy vet who has examined your buns to make sure you’re going in the right direction. To eliminate pellets, you need to supplement the things they need through different types of veggies so you can ensure they are still getting all the nutrients/vitamins/ect. that they need in their every day diets!
And I completely agree with Roberta on how to feed them — I have a bonded trio and we have three dishes (just in case) that we put 1/3 of the food in, the amount for each rabbit, and then let them go to town. My buns almost always will just crowd around the same dish anyways, but if one does get pushed out then he can always go to another dish to eat. All my buns weights are perfectly healthy also so I don’t think you have anything to worry about doing that way. Unless of course, one of them begins to get aggressive and vicious about it.