I live in Altinkum but love Icmeler. The two do not compare at all.
Icmeler is small and quiet, Altinkum is loud cheap and in your face. The bars in Dolphin Square are aimed at the younger generations but families are equally catered for. There are a few night clubs. The plus for me are the original Turku/Kurd misic bars. "Real" live music, genuine halay dancing. NO HASSLE at all in these bars but the square and 2nd beach hassle is a pain in the ass. The beach is superb,, sandy and shallow and soooo blue. There are plenty of places of interest a short way from Altinkum, Appollon Temple just one.
I hope you enjoy your stay. Please visit Yesilkent beach a small ride away on the dolmus, a delightful quiet beach with a nice restaurant Al Dente, You will find this a family beach with mainly Turk/muslim holiday makers. Brilliant place.