Handwritten letter?

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Totally overthinking this because I need to send a letter to accompany DS's questionnaires to the psychologist for his assessment.
I've got all the papers together but I'm assuming I can't just send them in an envelope to the secretary and I'll need to put a cover letter with them. Do I?
If so, can this cover letter be handwritten?
Or can I just stick a post-it on the first questionnaire saying they're DS's completed reports/forms?
Essentially all I need to say are Here are DS Name (d.o.b.) completed forms as requested ahead of his appointment on X.X.XX

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I would, it would put my mind at rest knowing that when it's received it will be easy to tie up with the appointment. Good luck with the appointment

Don’t forget to include any reference numbers that they have given you as well.