Draw baby related items like diaper pins, bottles, rattles, bibs, teats, blocks and cradles on 3×5 cards or colored card stock with a dark pen or marker. Make three matching items on as many scratch cards as you want winners, the rest of the cards should have 3 unmatched symbols. Using a silver wax crayon color over the drawings in a thick coating. You should be able to use a coin or fingernail to scratch the crayon color away to reveal the prize symbols below. Make sure to do a test copy before creating them all.
When the guests arrive hand each one a scratch card and ask them to hold them until everyone arrives. Give each guest a coin (a diaper pin works, too!) and ask her to scratch the silver off. The guest who gets the three matching items wins!