If you are wanting to make basically non dairy brews, you should get 'Water Kefir' grains, not 'milk Kefir' grains. The grains will not consume all the milk proteins, they will convert the lactose (milk sugars) that many folks are reactive to, making it more digestable for them. The protein content will be the same.
The flavor of non dairy stuff will taste better with real 'water kefir' grains, than with converted milk grains (personal opinion) and then if you have the right ones, you never need to worry about buying milk products you don't use in your diet just to maintain them.
That being said, you can convert 'milk kefir' grains to non dairy applications, but they usually stop reproducing and you will end up with a 'set' amount of grains (and won't be able to share them with friends, if you so desire). They wills still
convert the medium you are fermenting/culturing, but they do stop reproducing. The flavor isn't as good as a true 'water kefir' grain will make though.
If you are vegan, then don't bother putting them in milk at all, just put them in a sugar water solution, coconut milk, rice milk, fruit juices [grape is really good], etc. There is a recent thread about looking for 'non dairy' kefir due to lactose issues. There are several suggestions [recipes] for using the store bought powdered kefirs (a convenient way to have probiotic drinks, without having to baby grains...) to make fruit juice flavored drinks. Rather than repeating them all here, look it up, there are some really good suggestions there.
It's probably on about page 3/4 now....
I have started a 'water kefir grain' list. You can PM me for info about obtaining some, or you can get a weblink on that other thread for a site that sells them. We mom's here usually just charge a shipping and handling fee, (~$5.00) rather than the $20-40, you can pay for a commercial site to ship you some....
Good luck, and happy Kefiring!