Sounds like you are doing the right thing in charging them gas. If you are unsure about your skills and are still learning, the best thing is to be 100% honest with the "client" telling them that you are still learning.
Take the pictures, charge them gas, and learn as much as you can.
As for the pictures, great composition in 1 and 2. Needs more focus though, specially on the eyes which is key for portraits.
3 is too underexposed IMO, 4 is too overexposed
Overall pretty nice job, but as with all us new photographer wannabes, getting off Auto is the biggest step to learn. I was an auto shooter for a while and decided to f-it and just go with Manual.
If I am in an uncertain situation, I'll rely on Av (apeture priority) or Tv (shutter priority) when I need to get a quick pic and ensure the right settings for the right effect.
Come on...do it...you know you waaaaaant it.
