To make some things clear:
You currently have an older Mac with iPhoto and its own library? You have bought a new Mac or will buy one shortly and want to transfer the iPhoto Library to your new Mac from the older?
If that is the case, no need to involve the iPad, as you just can copy the
iPhoto Library file from the old Mac to the new Mac.
The
iPhoto Library file is located at
Macintosh HD / Users / YOU / Pictures / iPhoto / iPhoto Library.
You can either use an external storage device (HDD or USB stick) or your network or Target Disk Mode.
Mac OS X 10.5, 10.6: How to use Migration Assistant to transfer files from another Mac
If that is not the case, what exactly do you want to do? Get photos from your iPad to your (new) Mac?