To increase your dollars per conversion: You need to add other travel related services that pay an affiliate commission. Some examples are:

Taxi/Limo services Concierge Services Meal vouchers/deals Airline tickets Tour packages etc.

To increase your conversion rate: Get a valid SSL certificate and redirect all visitors to SSL via .htaccess Remove or minimize everything on the homepage not related to conversion (with the exception of the G+ and FB buttons). Use Groupon as an an extreme example of this. Start a Adwords remarketing campaign to follow your unconverted visitors as thet browse other sites in the Google Content network.

Those are the things that immediately come to mind.