At age seventeen, his mother signed enlistment papers on his behalf for the United States Navy and he attended boot camp at the Recruit Training Command in San Diego, California.

He also worked as an actor on stage and screen, including the titular role in playwright Jo Carson's Preacher with a Horse to Ride.

Through Mactavish Pictures, he produced commercials and corporate films for clients in various industries including Pepsi, Dun and Bradstreet, Deloitte & Touche, Pitney Bowes and The Gap.

Four of Lance's SEAL friends rode motorcycles from Virginia Beach to Alaska and back in thirty one days to honor his memory.

Mactavish then wrote, produced and directed MURPH: The Protector, a critically-acclaimed[14] tribute to Navy SEAL LT Michael Patrick Murphy, a Medal of Honor[15] recipient who gave his life for his men.

Following MURPH, Mactavish wrote, produced and directed Family Mission: The TJ Labraico Story,[16][17] distributed by Virgil Entertainment.

That same year he began development on Under the Trestle,[19] a true crime documentary based on the national bestseller of the same name by Ron Peterson, Jr.

He is an advisory board member of The Davis Focus Project, a non-profit that helps veterans overcome Traumatic Brain Injury, PTSD, depression, anxiety, and insomnia through innovative human performance protocols.