Littles Will Only Co-Front Rather Than Properly Hosting

My littles, aged 9, 6, and 4, will only co-front rather than really being in control. I've tried putting on their favourite movies and setting out games but nothing will work. Any ideas on how to let them come out fully?

Side note I've been thinking about: any experience on creating a tulpa to manage alters? Wondering if it's a good idea...

~Fisher