We have just come back from the Riu Park El Kebir 4 stars in Hammamet and had a fab time.Rooms were spotless,food was lovely and plenty of variety.Hotel is smack bang on the beach.I know its not an Iberostar like you mentioned but worth a look at.
We booked our holiday through Thomsons as it was way cheaper than anywhere else.

http://www.riu.com/en/hotel-riu-park-el-kebir-tunisia.html

hi we stayed in the sahara beach hotel in skanes. Hotel was nice and staff were friendly. great for kids animation team were really good. very roomy hotel with 3 good size pools. only problem i have with this hotel is that it is plonked right in the middle of no where and you have to get a taxi if you want to leave the resort. we went all inc and the food was adequate enough for 2 weeks.

recommend the hotel but not necessarily the area