It appears that you may have to pay the $100 per person upon arrival in Chile. I got the following information from the US Government web site: http://travel.state.gov/foreignentryreqs.html
CHILE - *Passport required. Visa not required for stay of up to 90 days. Entry fee of $100 (U.S.) charged at airport. Exit Requirement: Dependent children under age 18 (including the children of divorced parents) arriving traveling alone, with one parent, or in someone else’s custody, must present a notarized document certifying that both parents agree to their travel before the child will be allowed to exit Chile. This document must be notarized before a Chilean consular officer in the United States. For further information, consult the Embassy of Chile, 1732 Massachusetts Ave., NW, Washington, DC 20036 (202/785-1746 extensions. 104 or 110) or nearest Consulate General: CA (310/785-0113 and 415/982-7662), FL (305/373-8623), IL (312/654-8780), PA (215/829-9520), NY (212/355-0612), TX (713/621-5853) or PR
(787/725-6365). Internet: www.chile-usa.org
You could call the Chilean consulate to verify this information.