[clivehawkins]

Oh dear Ana,

Sounds like a tough group.
I find having mixed levels is more of a problem than mixed ages.
I'd suggest you spend a lesson or two determining each student's ability and then try to make classes within classes. In this way you can alter the activity to better suit each mini group.
For example, if you're presenting the past simple make sure you use easier verbs with the weaker groups, give them question prompts such as Where \ go \ last weekend?, give them picture prompts etc. With the stronger groups you can make them add a follow up question, ask them to include a list of less common irregular verbs, report back in the third person etc etc,

As for mixed ages, eventually they'll find some common ground: their home town, food, cinema, Portugal, today's weather, the teacher etc. it's not easy but I hope these ideas will help.
Good luck