If it bothers anyone that an 80 yr old woman had help with the cards or that the cards were preprinted and just signed I would say that person has a lot of extra time on their hands and is not a gracious person.
I too am impressed that there is still someone like you already thinking about thanking people when most people cannot even write an email or make a phone call to say Thank You.

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Eat Chinese food you'll be hungry in half an hour. Eat Italian food you'll be hungry in two weeks!