I would recommend single kayaks to begin. I think its important that you both find your center of gravity and your paddle style separately before tandem kayaking.
What type of water will you be going in?
Besides the practicality of learning individually before getting in one boat together...
I call tandem kayaks: "divorce kayaks".
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I have never enjoyed them, I find it frustrating and slower going. It takes patience to get in sync paddling both in style, in stroke length and speed. (I am not patient.) It also requires a distinct leader/follower relationship in terms of setting the course and speed.
I love the feeling of freedom and independence the kayak gives me, so the tandem always felt like work and perpetual negotiation, it took all of the joy out of the experience for me.
Occasionally I've even considered swimming back to shore rather than remain in a tandem.
But that could just be a
me-thing.
I know people who love tandem kayaking.