I hope some other people pop in to reply as well, but I will give you my n00b opinion that is based on *disclaimer*:
#1. Lots of "testing" of commercial GF beers.
#2. One successful batch so far.
#3. Two more in fermenters.
#4. Lots of reading here.
Sorghum gives beer a sort of metallic, twangy aftertaste that some people really dislike, and there are other drawbacks of using sorghum as your primary source of sugar such as poor mouth feel, poor head and head retention, etc.
Having said that, IMHO, most GF people (like me) are used to "weird" tasting food so I don't think they mind as much. However, I have been trying to reduce the amount of sorghum in each of my successive batches to attempt to achieve something even non-GF people might like to drink.
Also what you will find here is a lot of folks trying to add hops and other spices and flavors to compliment that twang. A lot of people have been quite successful in that it appears.
What you have there is a fine GF recipe that I bet your friend will be VERY happy with. YOU might not, but if you continue to brew GF you can experiment with other fermentables listed in the stickied thread above to achieve a more desirable result.
As far as honey goes for bottling, my experience reading here tells me that any fermentable WILL work it is just a matter of how much to use. Specifically, honey can be tricky because the gravity is different bottle to bottle and manufacturer to manufacturer.
Honestly, I am not sure why one would use this specifically for GF beers unless there was some worry of cross-contamination in the facilities that produce your typical "Priming Sugar".
If that's the case there is TONS of information out there about using simple table sugar (which is presumably GF) as a "Priming Sugar" or any number of other fermentables. From what I understand you could even leave some unfermented wort behind to prime with.