have you thought of hisaronu koy near marmaris its worth alook
http://www.marmarisyellowpages.com/1101.html
or type into google hisaronu koy

If a beautiful beach is your top consideration you couldn't get much better than Dalyan. It has a fabulous unspoilt beach, which is protected as its a nesting ground for turtles. The resort is on the river, and you have to take a beautiful boat trip to get the the beach which when we holidayed there we really enjoyed as it added another aspect to the holiday.
The setting of Dalyan is absolutely stunning, where restaurants line the river, with the rock tombs towering above on the other side. These are also lit up at night. There is also the ruins of an ancient city on the other side of the river.

It sounds the perfect place for you from the description of what you are looking for.

As Maverick says Hisaronu Koy is also lovely, its a very quiet small resort on the Bozburun peninsula. Don't get confused with Hisaronu near Olu Deniz which is very commercialised and probably not what you are looking for. Selimye is another beautiful small quiet resort near Hisaronu Koy and I believe Anatolian Sky go there, although they are not particularly cheap.
As you are particularly looking for a package I think you should have more of a choice in Dalyan that will be reasonably priced.
If you google Dalyan history culture you will get some websites with more info.

You could take a look at Oratkent on the Bodrum Peninsula, it is a small, traditional resort with a lovely beach. The good thing about being on the Peninsula is that it is easy to travel around by bus and nowhere is too far away.

Thomas Cook and Thomsons both go to Oratkent:

http://www.thomson.co.uk/destinations/europe/turkey/turkey-bodrum/ortakent/holidays-ortakent.html?ito=PPC-goo&itc=[holidays%20to%20ortakent]&gclid=CPXzhuHxj58CFSBk4wodgzD7JQ

http://www.thomascook.com/destinations/turkey/bodrum/ortakent/?lpsrc=Google&lpkey=holidays%20in%20ortakent&lppkid=p76693261&adv=tho&advid=15

Thanks for your suggestions so far. I will have a look at them now.