It's not too late! If you celebrate St. Patrick's Day with your family a fun surprise for your kids can be chocolate gold coins. I spotted them in the candy aisle at my local Walgreens. A small pack was $0.89 or 2/ $1.29.
One idea is to mess up the cushions and chairs around your house and hide the candy coins. Your children will be as excited as Christmas morning! They might assume some little leprechaun was searching for their gold there and dropped some!