i can totally see why you're overwhelmed! that's a lot to have right at the beginning. i've eased into the business gradually, and i still feel overwhelmed with 6 at times. i also had 2 brothers early on...not my first family, but close, and they were totally too much. i had to terminate them after not too long, partly due to their behavior, and partly because the dcm was ALWAYS late paying.
i believe that honesty is the best way to handle these things. there must be reasons why these boys are particularly overwhelming to you, and it's okay to admit that. sometimes dcf simply aren't a good fit. i think that's reason enough to explain to the dcm that it's best not only for you and the other children, but for her boys, that she find a place more suitable to their energy level or whatever. The key is to keep it as neutral as possible, and make sure to tell her that it isn't personal. as any parent knows, it's hard not to take things regarding our children personally.