I'm not one of the tandem gurus here, so I'll just address the saddle question.

If you have single bikes, are you comfortable on those saddles? If so, check your local Craigslist for the same models in used saddles. Otherwise, talk to Mel. A good dealer will often let you test ride models. Saddles are important, but very subjective. Much depends on how often you ride and how far you ride. Most folks find that when they ride enough so that their backsides have toughened up, they are more comfortable with firmer saddles than plush ones.

I assume you both wear padded cycling shorts. Essential to prevent chaffing if you ride anything longer than 15-minute trips to the park and back. Lots of options there, too.