Here's a vote for a small trailer.  We did a trip last year with 2 mountain
bikes, a 2-child bike trailer,sea kayak, windsurfer and rig, and all our
camping gear, stuffed in or on this: http://my.tbaytel.net/guskers/trailer.html

It's also served well on two Gorge (Hood River, Oregon) windsurfing trips
with 3 sailors plus camping and windsurfing gear.  That's about 4000 miles
round trip.  The only casualty so far is one blown trailer tire.  Another
plus is that flammables like the coleman stove and fuel are kept out of the van.

My converted 90 auto westy has no problem with it ... we were still able to
maintain 50 mph up the nastier hills.  Being that the vanagon is such an
aerodynamic brick on the highway, loading the roof seems to have much more
of an effect on both mileage and top end than towing a small trailer.
Highway mileage on the conversion hovers around 21 mpg (a 5 to 6 mpg hit)
while towing the trailer and driving 60 to 70mph.  Another plus is that
flammables like the coleman stove and fuel are kept out of the van when
travelling.   The trailer doubles as a black bear/raccoon proof food storage
bin when camping.