Show up dressed in street clothes, change standing in parking lot or where ever they have you parked. Thats reason number one why you have a towel in your ride bag.

Do the ride, no one really cares if you use a hydration pack or not, but for 28 miles you dont need one of the 100 oz type with a pack big enough to carry your gear for a week.

After the ride go back to your car. clean up take a baby wipe bath put on deoderant change into street clothes. then go eat.