we can't get the SIM card out of iPad 2 - there is a little whole but don't see a tray

Unless there is a visible seam that surround the hole, do not insert anything. The hole may be a microphone; if you insert a probe, you may cause irreparable damage.

If you are certain that you have a Cellular model of iPad, the SIM tray will be in the edge of the iPad. The visible seam of the SIM tray (which may require good light to see) will be about 10mm wide with a single hole positioned towards one end of the tray.

You need something small to put into the hole to release the SIM card tray.

Try a unwinding part of a paperclip to put into that hole to open the tray.