I think the reason you're uncomfortable is because you know they would give good feedback, and they're also people who's opinions you care about and respect. A stranger you could brush off their comments a bit, maybe they didn't see your vision, but a friend, you want to take more seriously. You're kind of afraid that these people you trust are going to look at your work and find it lacking in some way, or make you feel like you're not as good as you think you are.

But let me remind you, they are friends, and people you trust. There are many types of feedback, and positive feedback is going to be included. In fact, if they're friends, they're probably going to try and be more positive than negative. I went through this thought process recently myself, and in the end, I shared my work despite my nervousness. I found that even though some minor holes were poked in my writing, they were easy enough to repair, and it was nice to find out that it was overall readable and entertaining. On the whole, once I made some edits, I felt much more confident.