How do we handle pay for offsite meetings?

Q: “Our company holds quarterly meetings offsite during the day. Employees are not required to attend, but are invited and you could even say encouraged. Hourly employees who attend are paid if they attend; if they do not attend they are not paid but can take available PTO. Since the day has already begun for the employees, they need to travel to the event. Some drive themselves, some ride with others etc. The quarterly meetings are to communicate company updates, team building etc. The question is regarding travel pay. Can the company have those in attendance sign in when they arrive to “take attendance” and when payroll is submitted, add four hours to their pay for that time? The four hours would be based on the length of the event. This would be like holiday pay or a PTO day—added hours that do not reflect a specific time of arrival and departure, nor would it necessarily include travel time for either traveling to the event or back to the office at the end of the day. The reason to go back to the office would be if they carpooled. Otherwise they would go home from the event. If not, do you have other suggestions in lieu of paying employees for the travel time to the event?” – Christy, North Carolina