If i had Mo Health marketplace coverage, How do I find my premium % & how would I allocate that between my 2 children & i, having shared the policy with, for 5 months?

Normally, a parent who is actually on the hook for the premiums and the premium tax credit, takes 100% of the allocation, unless one of the children is employed and has money of their own.

You don't find the allocation; instead, you choose it in agreement with the other people on the 1095-A. Of course, if the other people are minors, it makes perfect sense that you take 100% and they take 0%.