For a few years, we had a friend that we gave gift cards to the grocery store and to Target (it was close to her home) at different times of the year.. Beginning of the school year and spring break. We mailed them to her. I actually had other people address them and mail them from other towns.
At Christmas we again mailed them. They were from Santa, one was from Mrs. Claus, and to toys R Us from the elves. We actually collected from friends and family and collected over $400.!
Again signed by friends and mailed from different areas.
She was in poor health had to have her legs severed and reset.. (yes really) , her husband had disappeared, she lost her job and her car had been repossessed, they wanted to take her mobile home, but she begged them to allow her to just pay something monthly. . She put herself through Health assistant classes and now works in a hospital helping deliver babies! She still has no idea where they came from.
So yes, anonymously will probably be the easiest way to do this.
You are good person to help them out.