Well if you want somewhere without too much nightlife I don't think Marmaris would be the right place for you, it is the nightlife capital of Turkey! The next resort along, Icmeler may be better suited if you are looking at that area.
I used to live in Turkey, near to Bodrum and there are some lovely resorts there you could look at. Gumbet is the liveliest place so if you are going mid season i.e. July or August it may be too busy, May, early June or September would be fine though. Turgutreis or Bitez are smaller, less nightlife but lots of places to eat out and have a drink. The beaches are nice too.
You have to be careful with AI hotels in Turkey. To get a decent AI you have to pay for it and they don't come cheap. If you get a bargain then you need to consider that you do get what you pay for and the quality of the accomodaiton and food wont be brilliant. Make sure you do lots of research on places like Tirp Advisor before you book.
Pamukkale is very nice but it is a long journey form the resorts. It takes 4 hours from Bodrum so probably the same or more from Marmaris. I did the trip some years ago and although I enjoyed it I wouldn't rush to sit in a coach for hours and hours again, maybe your boys would get bored with the journey.
I think a boat trip or a jeep safari would be more fun for you all. If you were to go to the Bodrum Peninsula, there is also a lovely castle in Bodrum, which is well worth a visit.
Wherever you decide to stay in Turkey I am sure you will have alovely time, the Turkish people are so friendly and they love children.