I would be pretty wary as getting the balance of low salt, protein and phosphorous would be difficult.
Raw carrot is often a snack which many dogs like.
Burns does a dried mixer food (Burns Hypoallergenic Mixer) which should be okay for a dog in renal failure. Only dried bits of kibble so not sure how your dog would take to that.
Another option could be to buy tins of the renal dog food. Slice from the can and bake in a slow oven until dried before cutting into small tidbits.
My dog would not tolerate the renal diet as it's known for being low in palatability. I now give them a mix of Burns fish and brown rice and hypoallergenic mixer which they love. This was the advice given from the Burns helpline (they did say a renal diet would be preferable but, where a dog didn't eat this food, this was an option).
My dog was diagnosed 2 years ago and has done well on this diet with his blood results showing an improvement :)
I also give him fish oils since his diagnosis from here:
http://www.mind1st.co.uk/Omega-3-Fatty-Acids-and-Canine-Renal-Failure.aspHTH and so sorry to hear about this in a young dog. I despaired after my dogs diagnosis but he continues to do really well so try not to overly worry :)