Take the money and RUN! That generous offer won't be on the table for long, I assure you (in fact, I only give it a 30% chance of him not backtracking on it) so the sooner you lock it in, the better.
Don't confuse fighting the divorce with fighting for your relationship. Seriously, he is MORE likely to come back if you DROP THE ROPE. The more you tug on the rope, the more he has to tug back and pull away. Once you drop the rope and APPEAR to be moving on, graciously, head held high, the more likely he'll start to question wth he's doing in the first place.
Get the best financial deal you can for you and your kids. Make that your number one priority. It doesn't mean your H can't change his mind or come back, but you have to keep the financials separate from the relationship stuff.