We have the same issue with the non-English speaking families and your probably right, I feel like it does contribute to the fact that there are people who don't participate. However, people need to be responsible for themselves IMO and they have ALL the school notices sent home in English so I wasn't concerned about that. If they can get translation on the other notices, why is this one different.
We just did the same thing, I sent home letters with all the kids which I personally handed out to them after school to collect for one big class gift. I wrote inside that it was completely voluntary and didn't specify any dollar amount. It said, "any contributions welcome" and explained that all of the money would be pooled to buy a larger gift item. I even went so far as to list a few options for them to vote on and said we would go with majority. I listed a personal gift card to a restaurant a personal gift like a basket with bath and spa items or movie themed basket etc or a gift card or item from the teacher supply store. I also told them when I would be shopping and asked if they wanted to go along. I added 2 other moms to the letter (after asking their permission) as people that they could give their money too or ask questions or whatever.
Only 8 families participated but we collected $130.00 and ended up with a $100 dollar gift card to a nice restaurant and a $30.00 gift from Bath and Body Works. We only included the people who contributed on the card. We went to each person who gave money and had them write a personal note and sign the card as well as their child sign the card. One day after school anyone that contributed to the gift hung around till everyone else was gone and we presented it to the teacher. I'm pretty sure she loved it but of course she said things like "you're all too generous" and "I am fine with chocolates or cookies, really".
Our goal wasn't to exclude anyone at all which is why we didn't suggest a dollar amount. We had people donate from $5 to $50 and I didn't tell anyone who contributed what. If someone would have brought $1 then they would have been included. However, I feel that the people who chose not to participate didn't need to be added to the card. We didn't give it to the teacher when any other kids were around who didn't contribute anyone who didn't wouldn't feel left out. Everyone was given the opportunity to contribute. Our biggest reason for doing this was to give the teacher something that she could really enjoy and use, after all how many boxes of chocolates can one person eat and how many coffee mugs do you need? Not that those gifts aren't hand picked and thought out but I know that if I was given those types of things year after year I wouldn't have space in my home to keep them all. Even when it comes to my own family I tend to give consumable items as gifts or experiences. I stay away from nick knacks and decorative items.