You are suggesting a compact between states, which requires Congressional approval. Article I Section 10 gives the states the right to bypass Congressional approval if they are actually invaded or in imminent danger.
Both of these conditions can be met. They are being invaded by uncontrolled illegal entry of minors and other non-regional foreignors. Imminent danger is possible with the serious diseases that these people are bringing with them.
Article IV Section 4 also grants the states the right to protect their borders from invasion, as well as any domestic violence that might occur as a result.
As you said, the states do not need permission from the federal government to protect the families of their residents. I'm pointing out the Constitutional provisions that declare this.
-PJ
I think the States have more than enough evidence to form a mutually protective compact. Waiting only increases the danger to the citizens of all the States.