I've been a class mom for my kids since they were in preschool and my personal experience is that you can send home the note but many parents will reach out and make the pledge but they don't follow through.
For example, my Kindergartner had a Thanksgiving party and I had a list of things requested, well I got 60 boxes of juice and and one tray of cookies for 25 kids. The next time I wised up and assigned stuff according to last name. I also had 95% of parents commit to purchase a book(that was used in the classroom) for teacher appreciation day so I ordered the books and sent home a letter stating the price was $x.xx please send in your $$ asap. Well, I ended up with 25% of parents who honored their committment so I ended up paying out of my pocket so the teacher would be able to replace the class copy of "Cricket In Time Square". I just learned my lesson to cover my end of the deal and not go above and beyond, very sad but true.