Yes, there are many activities that couples can do with a third person. Depending on your interests and what the couple agrees upon, some ideas could include going to the movies, playing board games or video games together, going out for dinner and drinks, attending music or art events together, going on a double date at a bowling alley or an amusement park, taking day trips to explore new places and attractions nearby, taking cooking classes together to learn a new skill, or participating in outdoor activities such as hiking and camping. Depending on where you live/what you have access to in your area you could also consider doing something like archery lessons or pottery classes. Ultimately it's up to the couple to decide what they would like to do with their third person!