Generally speaking, NIW is a lousy back up for a number of reasons. But I say this not knowing the merits of your situation, as your lawyer does.
But here are some things to consider.
Under current practice, CIS does NOT take away the H-1 time they have given you even if the 140 is denied.
An MTR is another dumb option in most cases. An appeal is the way to go. While the appeal is pending, you are permitted to keep getting H-1 extensions (an MTR does not give you that right). During that time you can work out other GC options. Consult with your lawyers and also get a second opinion.
The kids and your brother cannot do much. Your kids can petition for your green card only when they turn 21.