With an extra couple of days in Panama City, I'd recommend a visit to Panama Viejo, the site of the original city. In the late 1500s and 1600s, this was a major port and trans-shipment point for gold and silver on its way to Spain from Peru. The city was sacked by Henry Morgan in 1671.
Following the destruction of Panama Viejo, the residents moved west a few miles to a peninsula that could be better fortified against attack. This area is the location of the Presidential House, home of (you guessed it) Panama's elected leader, and the old fort, or Casco Viejo. This area of Panama City is enjoying a renaissance these days, with lots of cafes and night spots to go with the colonial archetecture. Be sure to see the gold altar in the Cathedral San Jose.
For a pleasant alternative to staying in Panama City, consider the Canopy Tower Lodge, an ecotourist lodge on top of Semaphore Hill in Soberania National Park. The lodge is about 45 minutes' drive from Panama City. the lodge is based on an old radar station, and offers panoramic views of the surrounding forest as well as a convenient base for exploring the Panama Canal and the famous (to birdwatchers, at least) Pipeline Road. Here's their web site
http://www.canopytower.com
March is prime time for birdwatching, so rooms at Canopy Tower Lodge may not be available. I think they might be willing to let you camp in the Earthroamers, however.
The company that runs Canopy Tower Lodge has a second lodge called Canopy Lodge. It's located high above the town of El Valle de Anton, about 60 miles (maybe 2.5 hours' drive) west of Panama City. El Valle is a vacation destination for Panamanians, and it has a productive artists' colony. The Tower Lodge was constructed a few years ago with ecotourism in mind. I have not stayed there myself, but reports from friends have been enthusiastic. The web site is
http://www.canopylodge.com/
While in El Valle, take a ride on the zip line adventure operated by Canopy Adventures. These folks probably could point you in the direction of some off-road driving routes if the Earthroamers are not packed into cargo containers yet.
Panama is a great place to visit for vacation, particularly as an introduction to Central America. It has excellent infrastructure, interesting natural resources, friendly people, great food, and plenty of historic sites. The local currency is the US Dollar. Non-stop flights are available from Miami, Houston, Dallas, Atlanta and Los Angeles.
Chip Haven