I'm not sure you could even get Cavani. He signed a 5 year deal last summer, and how important is he to Napoli? He has been the focal point of the attack which has propelled them to the CL. He works so well in their system, and they aren't in need of cash. I don't think they would sell him, seeing as there is no obvious replacement for their style of football, and the cash they would lose missing out on the CL.
I think City's problem is it hard to decide who you keep
Ade- I'm not sure of his top level goalscoring, even as Spurs this season his scoring rate hasn't been that of the striker City need in that central role. Also his relationship with the club is questionable
Balo- Talented, but I don't know if you can trust him. He's got a bad agent. I don't know if his future lies in English football.
Dzeko- Needs to play centrally for me, I think he could be the striker you need.
Tevez- No way. His relationship with Mancini is questionable for sure, he's 28 now, the oldest of the strikers. He's commitment to the sport is questionable.
Aguero- Definitely keep, although I don't like him played centrally.
I'd keep Balo(assuming Mancini stays), Dzeko, and Aguero. 4th striker would be good, but you can't have 4 big names on big wages.