I think a card is perfectly OK.
It's a gesture of appreciation, after all. I had the same thought last year, then my counsellor gave me one first, so I had to wait until the following week to give her one.
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'Somewhere up above the great divide
Where the sky is wide, and the clouds are few
A man can see his way clear to the light
'You have all the grace you need for today, and today is all that matters.' - Steve Austin