You will get lots more tech points by using your kids to pick up the artifacts. You get 100 tech points for each one that you've already picked up once, but I think that I got 500 points for getting a rare item more than once! You only pick up a collectible once, and it shows on the screen, but you'll need four common shells (for instance), four uncommon ones, and four rare ones. After picking up one shell, the next one that is identical to that one will just add to your tech points.