Inside your Pictures folder is the iPhoto Library, Finder > duplicate it and copy it to a external drive large enough to handle it.
Then connect the drive to the new machine and copy it into the Pictures folder there, renaming it without the "copy" portion and start iPhoto.
It will sense it's a older copy and update it.
If you already have pictures in the newer iPhoto Library on the new machine, then don't replace the new with the old one.
Rather right click on the old iPhoto Library Copy and "show package contents" inside is a folder called Originals, duplicate that out and import it into the new iPhoto program, it will place the pictures into the new iPhoto Library.