What power class does an iPad and an iPhone have?
The radio frequencies and they respective power are regulated by official sources. In the USA, you will need to go to the FCC web site to get precise numbers for the radio power output.

In order to search the FCC OET Equipment Authorization database, you will need the FCC ID of the device you want to lookup. 

All devices that use radio frequency spectrum are required to print their unique FCC ID on a label on the device. 

It may also be printed on a separate document that accompanies the device. 

Example for iPhone 4S WiFi radio.