Best diaper bag for 2!?

My son will.be 2.5 when baby is born so we won't need alot for him. But I've slowly started training him so I would assume I would atleast need extra clothes just incase (maybe pull ups depending on how far we get) and snacks I guess haha. But I have a decent size one and always remember it being soooooo full.

I'm also going to be breastfeeding, and we take alot of day trips (our families are about an hour away), so either a bag big enough to bring a pump if needed or maybe a decent pump with a carry bag?