Best diaper bag for someone with 3 kiddos?

I have twin 3 year olds and a 3rd baby due in August. I feel like I need something to accommodate the baby (potentially bringing bottles and formula with us places, toys, changes of clothes, burp cloths, etc), and my twins (changes of clothes, small toys to keep them occupied, maybe an activity book or two). Any recommendations on backpack diaper bags you think I can fit my life into?