I am planning on making a switch from AT&T to Verizon. We have multiple iPads which are wifi+cellular with AT&T. Will these be compatible with Verizon? Also, do the new Verizon iPads (4th gen and mini) come with a sim slot? If so, does the Verizon data on the iPad work via the sim or CDMA? If they have a sim slot, are they unlocked? Thanks in advance for your help.