In reference to the original text on the coupon (当日カップル無料券 - appointed day couple free ticket), it read more like a promotion for their grand opening. I ran out of space when replacing the text; my apologies for ending up losing that point with my version.
In any case, with that promotion, though, the cafe gets two people to come, hook them both, and they'll want to come back - and for that they'll have to pay, lol.
And I think the implication of kiss was Lisa getting a little ahead of herself, to be honest, rather than Yukina offering a suggestion. That's just my interpretation of the dialogue layout, though.
