That's a good summary. I think the best idea for signalling wanting to leave would be, if it's alright with you, coming over and touching your arm in some manner. Pretty to the point but doesn't require verbal reinforcement.

[Attractive young object of affection? He smirks and finishes his tea before standing.]

We'll need an affectionate diminutive or other affectation. So you can call me something to get my attention if you must.