Yay! Welcome Jody!
Ideally each card would have both an envelope and a clear jacket of some sort - preferably clear envelopes or something less bulky than a ziploc.
This is so that the patients and their families can flip through the basket of thousands of cards without damaging them
But just do what you can and what is economically feasible for you. The most important part is sending this paper joy to the hospital
I'm so glad you will be playing with us - you are going to have SO much fun with us!!