2 shops you can try asking would be The Bike Doctor (thebikedr.com) or JVBike (jvbike.com) if they're willing to take your bikes. It can be tricky receiving bikes especially from another country due to customs issues and stores sometimes don't want to deal with them. Why not ship your Raleigh Tamland 2 to your friend's place and then drive to these 2 places and have them assemble it? The Bike Doctor has both road and hybrid bike rentals and they are a somewhat touring centric store than JVbike. In fact, why not just rent 2 bikes and have them configured with low gears. San Juan island, except Lopez, is not exactly flat as pancake. The other stores in Vancouver are more road performance oriented or mountain bike oriented. And just across the street from The Bike Doctor is the infamous MEC store!

Both of these stores can easily be accessible via dedicated bike paths and the Canada Line train and the train starts from the Airport. Very convenient. The same train takes you to Bridgeport exchange hub where you can take the Tsawwassen Express line (Bus #620 ) which has 2 bike racks upfront. From Bridgeport to the ferry terminal would only take about 33 minutes or so. I assume both of you will be taking the Sidney BC ferry to Friday harbour? That's an afternoon ferry so you have plenty of time and essentially don't need a car to go to the ferry and pay for parking fees. I've done this trip a few times already this format.