Yes - Indubitably!
No - U.S. Citizens are not required to obtain a travel visa. The US passport will serve to afford travelers up to 90 days in the country of Colombia.
Don't worry! We will be doing our best to make sure everyone is fed while they are here. You just worry about the flights! We will also be organizing Airbnb locations to share with other friends and family to keep lodging costs low ( ~ $50 per person - per night).
We have an idea of having everyone dress in white for the wedding (if possible). Nothing too formal. Even the groom will not be wearing a tie. Say comfortable - semi-formal. Additionally, you should bring your swimming attire for relaxing in and around the pool! You should expect warm weather and it would be good to bring a light rain jacket.