Tropicana Rewards has a B1G1 for Tom Sawyer's Cave (something I definitely plan to do!). This is a savings of $15.95 for everybody over 12 and $9.95 for everybody 8-12 (it's only $2.10 for children under 8). To get the rewards, go to this website and register. Then you can enter codes from the lids of your orange juice (get double points if you purchase the OJ at Smith's - put Kroger as your store and let them know you used your card). There are a couple of "freebie" codes (the site divides the codes in half):

BLOGG-HER11
FBOOK-TROPI
MOMCE-NTRAL

Then, before the trip make sure to print off the coupons (they're only good for two weeks after printed so don't print too early). Just "explore rewards" and type in zip code 63401 (Hannibal). This is the deal under "Amusement/Water Parks." Hooray for coupons!