Bedtime for 2.5 year old

I'm trying to create a healthy bedtime routine for my 2.5 year old. We do dinner, bath, brush, book, and rock to sleep... except he won't go/stay asleep. My husband and I go to bed at 12 to spend time with each other because we also have 4 month old twins. But we want our babies to all have structure. The only problem is we can't get our 2.5 year old to go to sleep on his own. We've even accepted that he's going to eventually get up and get in the bed with me and the babes or with Sr. on the couch. But we just need him to go to sleep at 9:30. How do you do this?