Bull wants me to suck his dick[cuckolds perspective]

So my gf and her daddy have been fucking for almost 3 years now. He’s been actively trying to breed her whenever he flys into town and we’ve gotten to the point where I actively call him daddy also and he literally treats her like fuck meat, comes over says nothing besides “who’s pussy is it” or “you missed fucking big dick didnt you” etc.. then leaves without a word just uses her. Now he’s been telling me when he blindfolds her that he wants me to suck his dick while she rides his face so she doesn’t know which I do appreciate because I’m still a shy cuck ????. I’ve drank his cum from a cup he left on the doorstep about a year ago and I did NOT like the taste but did it to submit because he is daddy after all. I say all that to say this, I’m nervous! I feel like I’m going to be bad at it and I’m not trying to have my gf see me do that so the blindfold is super necessary for her. Idk what to do. I need advice. I want to please daddy and I’d say I 75% want to suck his dick but the thought of her noticing or something worry’s me.