Guests are happy to get a text that helps them: the ticket, the car-ready alert, the receipt. They are not happy to get marketing they never asked for.
Record consent before sending anything. A clear toggle at check-in that shows the exact wording is better than a pre-checked box.
Name the venue in the first message, tell guests how to stop messages and honor STOP at once. Keep texts short and free of offers.
This is a summary and not legal advice. Check the rules that apply to your business with counsel.