As far as I can see in my IFTTT account I can only enable motion detection for a single camera or for all cameras. It doesn’t show my camera groups in IFTTT. There is a Wishlist topic requesting built-in geofencing for multiple users; you can vote for it here:
If that feature were built-in it would also solve your issue with the motion/contact sensors. Without built-in geofencing you will unfortunately have to set up one IFTTT applet for each sensor.
Regarding IFTTT location on multiple devices, IFTTT doesn’t currently have a good way to deal with multi-user/-device locations. You could probably disable location permissions on the iPad or whichever device you don’t want to use for your location. I have multiple user geofencing set up using Apilio.io, but there’s a pretty steep learning curve for that configuration.