Special needs ring bearer: need advice

FH's nephew is one of our 2 ring bearers and he has autism. It was never a question for us though, he was his nephew, his sisters are flower girls and we wanted to include him. Over Christmas, FH's SIL (child's mother) kept saying "don't feel obligated...he's a lot to handle...he's a handful...don't feel like you have to." I never felt obligated, just wanted to include him and to be honest, I've never witnessed him have an episode. He's always been a really good kid. Apparently though he's a runner and has meltdowns. At Christmas when it was 72 degrees out, we had the front door open but we kept keeping watch to make sure he didn't run out. Our wedding will be loud, crowded and our open space venue will have open doors with access to a river. Now I'm wondering if it is a good idea to include him, based on that reason. I don't care about even numbers or things going right down the aisle, but I want him to be comfortable and I want his parents (father is BM) to have a good time