Just a little thing I learned years ago.....if you buy one of those soap travel containers down the sample aisle at Target (holds soap so it won't get soggy after using it) it makes a GREAT mini first aid kit. You can put various sized bandaids in it, a tube of neosporin, and a few alcohol or other antibacterial wipes. It shuts nicely and fits in just about any size bag.
We carry Clorox wipes, regular antibacterial hand wipes, hand sanitizer, tums, ibuprofen and other pain meds, a few snack size bags of gummies or crackers, a tube of those 1.00 light up bracelets/necklaces from Target, our little first aid kit (mentioned above), Passporter and an extra pair of socks for everyone in case our feet get wet in the rain. We also put quite a few empty ziploc bags in there in case we have leftover cookies or krispie treats from lunch/snack that we can store for later. And the ziploc bags work great for putting wet stuff in (wet socks if it rains...etc.) Oh and the most important...a tide pen LOL All that food, one of us is bound to get something on us and I hate the thought of getting pictures for the rest of the day with a big pizza stain on one of their shirts LOL
We put our poncho's in a big gallon size ziploc and store those under the stroller along with our stroller rain/wind cover. Everything else fits in the bag we carry.