I have seen this twice on social media already today.

Do NOT do this.
The whole point of isolation is to isolate people.
You can transmit the virus prior to symptoms (esp kids who tend to be much less sick than others.)
Virus can live on surfaces for 46 hours at least.
Do not mail your child’s plague bomb to nursing homes (or anyone else).

Do not drop off cookies. Do not send paper.
It’s the 21st century. Use e-mail. Skype. Facetime. Or, heaven forfend, pick up the phone and call.

[Stats source:

No Coronavirus Break Playdates. Here’s Why.

Addendum: here’s a paper on the matter. Virus can live at least 72 hours on stainless steel and plastic; 24 hours on cardboard.