Booking Engine for Tours site

I am developing a website which will allow customers to book? tours and services in the area they are going on vacation. It will be initially launched in one area of Central America, but will need to be expanded as the business grows to other regions. It will need to accomodate merchant account services so the customer can pre-pay and reserve a tour or service. Because of the nature of the tour and service business the user will choose a range of days for a particular tour or service, there will need to be a few drop-down categories for narrowing down the service but most imprtantly? we will need a large 'comment box' for the guest to describe what they are looking for especially since some tours are customized, as well as some customers not knowing exactly what they want, we can assist them based on what they write.