Hi so sorry for your loss did you and the children receive bereavement counciling. The school can help put this into place. As reward system try not to offer money as some weeks you may not be able to afford it. I used video eve with pop corn they both choose a film and watch them as a family. And allow them to stay up an extra 15 mins for youngest and 1/2 hour for eldest. My now 16 year old when she was younger and couldn't tell the time I used to you can stay up till 8.30 she was so excited poor thing didn't realise that was her bedtime anyway but she was so busy school, drama, dance, singing, speech and drama,. But if she was a little monster it was bed early and the 2 times I was called into school through unexseptable behaviour shed be banned form electronics ie TV and bed early for a week. But try putting little one bed earlier than the eldest as she needs quality time with mum even if it just snuggles in sofa or pamper eve x