Pizza parties, t-shirts, and ice cream sundaes are nice things to do, but don’t confuse the increased loyalty and happiness they might provide with “engagement” leading people to higher productivity and increased retention of people. Employee engagement comes from the satisfaction of personal growth and having done a good job.
Instead of trying to engage people, try better matching people to jobs where they feel challenged and stimulated, and where they feel that they are learning and growing. Make sure they understand how their work contributes to valuable company achievements.
Employee engagement is a result of doing many things right, and most of all creating the conditions where employee can excel at their jobs. Keep doing the cookouts if you want – they can be beneficial, but that’s not what will engage people.