We used a tandem for 5 months for her to get a good start on her paddling form and core to get in shape, then sold the tandem at a huge loss to get a boat she was comfortable in.
From a pure cost effective point of view getting 2 entry level kayaks will cost about the same as a decent tandem, and you can get boats that fit you much better.
For a decent general use kayak for lakes and lower class white water, Dagger Alchemy (S or L) may be a good place to start looking. Your best bet is to go to a shop that specializes in kayaks and just try some on. Just like shoes or clothes, everybody has distinct likes and dislikes. There is no substitute for human contact and direct advice.
This forum is a great place to get advise and knowledge from a vast experience pool.
There is a lot of water out there, and lots of different ways to play in it.
EZ Launch™ Kayak & Canoe
Touring Kayak Paddles
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