We just use a regular old backpack! Diaper bags look cute but there’s too many pockets and they are heavy. Plus backpacks have comfy straps.

Used to use a 25L dakine [like this](Dakine Campus M 25L, Electric Tropical, One Size https://www.amazon.com/dp/B0949CWF1X?ref_=cm_sw_r_apin_dp_1D3XKZMWY9SH1YZJGZNQ) that has a cooler pocket in front. Was a little big for one kid.

Diapers/wipes/pad went in the laptop sleeve pocket, milk in the cooler pocket, had zipper bags for a change of clothes / snacks. Stuck little things where you’d put pens.

Now we just use a 12 or 15l one since we’re just carrying snacks, change of clothes etc. Potty training rocks!