Understood.. This can usually be cured by the following.. Lets try all steps on one device first, phone or ipad.
First, go to settings, network, and tap reset network settings. Then, press and hold the sleep/ wake and the home button for 15 seconds till the apple logo shows and the device turns off. Then release the buttons. If the ipad doesnt turn back on by itself, press the sleep wake button to turn it on normally.. Once booted, go to settings, wifi, and reconnect to your wifi network.
Then, see if the canon print app can see your printer. If not, uninstall the canon print app, and then reinstall it.
Then turn the idevice off and back on again and see if the canon print app can see the printer.
If this works for one device, repeat those steps on the other i device. Whatever the results, please let me know in detail so I can assist you further or please reply and submit a 5 star rating to show I was able to assist you.
Senior Technician and Network Switching Systems Operator / Maintainer.