NiceSwan,
Me and my girlfriend (31 & 24) have visited a few resorts over the last three years that might be suitable. We usually look for somewhere lively but not over the top. The last thing we want is an 18-30s style resort like Laganas, Faliraki, Kavos etc but we do want plenty of bars and restaurants to choose from, maybe even a nightclub or two.
Last year we went to Hanioti, Halkidiki in June. It was reasonably lively - will be obviously busier when your looking to travel - and our nights were generally as lively or as quiet as we wanted. On the quiter nights we found a few nice small bars down near the beach to chill out in (one bar is actually on the beach with chairs pointing out to the sea lit up by lanterns pushed into the sand), and on the nights we fancied a good drink we headed for the square where most of the action takes place. You will find a number of places to eat and drink, some places playing music, some not and there are also a number of streets leading off from the square for more choice. We were very impressed by the restaurants in the resort, all of which were of a high standard. There were a lot of couples of all ages in this resort ranging from ealry 20s to 60+ as there really is something for everyone.
We've also been to Sidari on Corfu. This is generally regarded as the second liveliest resort on the island - most of the 18-30s crowd go to Kavos - and again we found a good variety of bars and restaurants. Like Hanioti we found we could choose what sort of night we were going to have. There are a number of 'disco style' bars and clubs but also quieter options and bars with live acts on - singers, comedians, pub quizzes, karioke etc. In my opinion Sidari is livelier than Hanioti - there is basically one long street that runs through the resort lined with bars, restaurants, shops etc - but if you stay in the Canal D'Amour area of the resort or in accomodation well away from this main road you'd be far enough away from the centre to not hear any noise if you fancied an early night!
Also been to Argassi in Zante. Similar to Sidari in that there are plenty of bars, restaurants along one main road. Again a lively resort but not too full on. We got a taxi to Laganas on one evening (about 15 euros) and had a really good night but were glad we weren't staying in this resort. A bit too hectic for me now I'm getting on a bit! Argassi despite being lively/busy was much more relaxed but we did go first week of September so not peak season. If you or the mrs like a nice beach I would avoid Argassi as the beach is very small, narrow and in my opinion poor.
Hope this has helped a bit. If you want to know anything specific about any of these resorts just ask and I'll do my best.
Steve