[Effendi]

Wind has almost 1800 only in Turin (plus WCDMA), and it has less customers than the other 2. Also it's out of the main "network alliances", so most roaming people will probably be on TIM and Vodafone (anyway many will use Wind as well). Surely penetration in old buildings is worse with 1800, but that shouldn't be a problem at the Olympic Village, which is surely perfectly covered by all 4 operators.
I think you won't go to many "rural areas", you'll probably go to the mountains where the Olympic games will be held, and again you'll have good GSM coverage, mostly 900MHz by all 3 operators, plus probably some 1800MHz added for the event.

So I think you shouldn't have coverage problems with any of the 3.
The 25 euro starting kit with 26 euros of credit is something I never saw, and never even heard of it. The starting kit at 5 euros with 5 euros is quite common with Wind and Vodafone, but usually on Summer or Christmas holidays. In February you should pay it 10 euros. I think TIM is sponsor of the Olympics, so maybe TIM could do some promotion.

Yes it's true TIM invented prepaid cards, but it was Omnitel (now Vodafone) who had the good success with them, offering the SMS service which TIM didn't have.