Uber vouchers

Has anyone used Uber vouchers to get their overnight wedding guests from the hotel to the venue and back again at the end of the night? Looking at our guest list it will probably be only 10-15 couples and it seems like having an actual shuttle service might be more money. I know that you don’t have to pay for what’s not used but how did it work? Was it a code you could give out to people or did it have to be emailed to them? I’m thinking about the unexpected guest who might want to Uber because they enjoyed the open bar a little too heavily and I don’t want to worry about having to email them the code last minute.