Your answers should be answered here:

http://beta.alitalia.com/eg_en/infor...0-12-anni.html

Skyteam Elite Plus:
One free extra bag: if you are traveling in Economy or Economy Premium, maximum weight of 23kg; if you are traveling in Business Class Medium/Long Haul, maximum weight of 32kg. Moreover, in case of purchase of a Light Fare, the baggae is free (1 baggage 23kg) in addition of any sports equipment