Wrt54g dual outdoor antenna?

Hello
I set up a PublicIP hotspot connected to Linksys wrt54g with ddwrt software. This hotspot is at a campground. I had a problem with range so I boosted the xmit power to 98.
I also added two Linksys 7dbi high gain antennas to the wrt54g. The RV spots are no more than 350 feet away, but there is a wooden bath house in the path between the router and a couple of the RV’s which is causing a connection problem.
I have been looking for a fix for this problem, and am some what confused as to the antenna situation.
The router has two antennas, so I have been looking for an outside antenna for this router with two connections. I would like to mount the antennas on the roof. If I run a long cable(100’) between the router and antenna, do I need some kind of booster? Do I need two cables and antennas or can one be connected to the other?
Thanks in advance for anyone’s help!!