A Tandem is a great way to tour for two people. The weight of a tandem is a lot less than the weight of two bicycles, so you go faster or can carry more luggage. Also you never have the problem of your slower companion lagging behind you (or your faster companion racing off). Click here or here for some basic tandem riding tips or here for a video look at a tandem bike

Dawes are the classic tried and tested touring tandem manufacturer and come in a range of frame sizes from the smaller adult+child-fit 20"/13" (an option for the duet twin) to 21"/17"