Yep, what Zorba said. The only times you need to worry about a charger is when it's not powerful enough -- for instance, using a 40W charger for a 15" MacBook Pro (which is 85W). Drawing too much power from something is very dangerous.
Conversely, you can easily use an 85W charger with a MacBook Air -- it'll only draw as much juice as it needs. Same applies for all electronics, really, and the same for your iPad.