Me and my GF (34yr & 25yr) have just returned from a 1 week holiday in Lassi (23rd-30th July) and we loved it. Some folk have said that Lassi is too commercial etc... but we didn't find that. There are in excess of 15-20 restaurants and of the 8 or so we tried we didn't have a bad meal.
Regarding bars there are over 15 in the resort and a majority of these are great pubs which all have nice gardens/sea views where you can sit and chill out.
For the dancers there is club which is open until 3am or 4am, but don't worry about any noise as it's all sound proofed.
If your a sun lover than you'd be in your element as within a 5-10 minute walk from the centre there are over half a dozen beaches and coves to visit.
As mentioned in earlier messages, Argostoli is only a 25 min walk and there you will find a whole host of restarants and bars, which are especially good around the main square. Also in Agostoli is the Lithostrato which is the main street for all your shopping.
Overall I would say that Lassi is an excellent all round resort for both families and couples of any age.