I don't think that would apply in your situation since you will just be checking email on the iPad using your own iCloud accounts. This lockout has to do with downloading past purchases.
To the best of my knowledge, the 90 day lockout occurs only when you switch Apple ID's and then download a past purchase with the ID that you just signed into. When you download a past purchase with a different ID, that associates the device with that ID. The same also occurs the first time that you download a past purchase on your own new device using your own ID.
Apple implemented this feature so that a user cannot allow other users to download their purchases for free by switching ID's, without someone paying the price for that, and the price being that you will be locked out of your ID for 90 days.
You may have read this before, but if not, take a look at this.
Manage your associated devices in iTunes - Apple Support