iPad mini and iPad 2 very slow after upgrade to ios7-why.

Have you tried restarting or resetting your iPad?

Restart: Press On/Off button until the Slide to Power Off slider appears, select Slide to Power Off and, after the iPad shuts down, then press the On/Off button until the Apple logo appears.

Reset: Press the Home and On/Off buttons at the same time and hold them until the Apple logo appears (about 10 seconds).

Two things that might help. Reset all your settings and reset the phone. Use the Settings app to reset all settings. Settings > General > Reset > Reset All Settings Then reset your device. Press and hold the Home and Sleep buttons simultaneously until the Apple logo appears. Let go of the buttons and let the device restart. See if that helps.

You can also change various settings to cut down the amount of activity in your iPad. Turn off Push of emails and especially look at Background App Refresh. Turn that off for all apps you really do not need to be refreshg in the background.