Is your 16-yr old son going to still be backpacking with you when he is 18+? Are you always going to want to backpack with another person? Do you want to fit any gear inside? If so the 3-man tent is the choice. If you ever decide to solo, it is too heavy. There is no standard for what constitutes a 3-man tent. Look for the actual dimensions. Look at shoulder location width, sit-up location height and length. Some of the narrow 2-man tents are designed to sleep head-to-foot. I doubt this is what you want to do. There are some 2-man tents that are essentially the same dimensions as 3-man tents. LOTS of 2-man tents are really not much bigger than a solo tent. There are double-wall tents and single wall tents. Single wall tents are lighter, but you will have condensation on the inside roof. Also, do you need a 3-season tent or 4-season tent? Few people need 4-season tents. You may want to rent tents until you get it figured out.

Have you considered a tarp?