I think the pretend friends could very well be assigned helpers. Since reading Bruce's books about helpers and guides on the other levels, planning commissions, time/line event planners, it's a very benevolent organized universe despite we may feel separated from all that is good at times. I conducted my own experiments and found the helper spirits do exist and children are especially close to this other world as their unconscious minds have not closed off completely with belief systems yet. I see nothing harmful with pretend friends.
start listening in to their conversations to see if your children truly are benefitting. its your job to protect them, but if they are benefitting then there is no harm.
love, alysia