I agree. This is a case of be extremely cautions and verify.
They'll have to be monitored 24/7/365+ to be sure they live up to their agreement.
A rapid ready force should be established.
Sooner or later Islamic doctrine will get them fighting again. If they really wanted to succeed in destroying America they would support the Democrat party.
I think the best solution is to make sure the population becomes half Sunni and half Shia. Then they will become too busy killing each other to bother attacking America again. If any side starts to overwhelm the other side supply the losing side with arms and keep the battle going on for the rest of time.