Sounds better than our first tandem. We started out with a Schwinn Twinn coaster brake bike that I rebuilt several times and eventually turned into a 60 pound 10-speed. At the time it was all that we could afford so my wife and I rode it all over including several hilly 50 miler rides.
My advice is to keep it stock and enjoy it for what it is. You can spend a ton of money trying to upgrade that bike but you'll always be hampered because it has a water pipe frame that probably doesn't fit either one of you well. If you and your wife get the bug, turn it over and buy yourselves a better bike.