Let's see if we can distill this down a bit.....
Prefer tube and fabric....but no welding skills....cheap to store and operate.....but wife wants four seats....
Uhhhhh, something has to give here....
Perhaps, if the four seat option can be eliminated because that takes you into a far different class of aircraft, a wood aircraft might be your best option. Wood is pleasant to work with, only requires basic shop tools, can be purchased in small and relatively inexpensive quantities, and can be built from either plans or kits. It also gives you the fabric experience without the welding. There are many great wood aircraft available, many with decades of field history. Wood is a great material to share with children, they relate to it (big model airplane!)...and it makes the shop smell nice!
Just be sure you select an aircraft that will accommodate two adult-size occupants....your son won't be a little kid forever. This may be a challenge since many wood aircraft were designed before adults became bubba-sized.
Best wishes, and enjoy the journey!