There are lots of activities you can do. In most classes, even if there were a lot more students they would spend quite a lot of time working in pairs, doing roleplays, games, interviews etc etc. But in a class of two you also have the advantage that you can have them talking directly to you without cutting down on studet talking time and risking people being uninvolved and getting bored. Try
here for lots of speaking activities, most of which would be suitable.