I agree, but it still should not be tolerated. Try start giving them warnings, and if they don't listen take their favorite toy or things away from them one at a time, if they are good boys, they can earn them back. This usually helps with my boys. Good luck. Sorry about ur loss.
sorry for your loss, it also going to be difficult for her children because they've lost their mum and no one will replace her, you should expect naughty behaviour with such a great loss they dont know what to do, its the way they show their anger and emotion, it will pass in time