My DS starts school next term and my newborn wi...

My DS starts school next term and my newborn will only be a few weeks old. I need to get all 3 kids out the door and at school by 8.30am. During the first few weeks of school i will be hanging around for a while, not just a quick good bye. My question is if bubs is an hour off feeding, should i just give a "top up feed" to make sure i can concentrate on sending my DS off to school?? How does it work?? I know my DS is going to find the transition a difficult one so want to make sure i can take care of him as much as possible without a screaming hungry bubs. Any advice would be appreciated :)