For a connection between buildings I'd suggest using directional antennas. It would be much more reliable and offer better throughput than using omni-directional repeaters. Also each repeater you have results in a 50% loss of performance as it needs to send/receive twice as much as a normal access point.
I'd put something like this:
EnGenius Outdoor Wireless Access Point / Bridge 802.11B/G 108MBPS 600MW W/ Dual Antenna PoE Support - EnGenius - EOC2611P on the outside of each building, facing towards each other as best as possible.
This would give you a wireless bridge (basically same as running an Ethernet cable between buildings). Then on either end, you'd plug it into a more standard WiFi router to get coverage within the buildings.
Just make sure you use non-overlapping channels. So say you make the wireless bridge as channel 1, then make the WiFi routers in either building run on channel 6 or channel 11, this should decrease the interference.