We have two kids (now 10 and 12), and if we're with them, we'll carry a backpack -- raincoats/ponchos (if weather needs it), bottled water (more in summer, less in fall/winter), maybe autograph books, purchases, and maybe a sunglasses case if we're planning to be in the parks late, although lately I have tried to rely on a strap/cord instead of an actual case. While we have a nice SLR camera, we tend to use our phones or a PhotoPass photographer. Depending on time of year, we might have a little bottle of sunscreen, but in February, I would think you could avoid sunscreen or at least slather on a little in the room in the morning and let that carry you for the day.
With that lengthy introduction (sorry), we recently went for the first time without the kids (primarily Food & Wine), and I cannot begin to tell you how refreshing it was to head to a park with no bag whatsoever. There was no rain forecast, so that helped. It was also early October, and this year at least, it was rather hot, so no need for extra layers. Had sunglasses and phones (cameras) attached to us or in a pocket. I would start a trip to a park just carrying a bottle of water, but when gone, I just tossed it.
To be fair, my wife still felt like she needed a little bag of some sort, so once or twice she carried one of those drawstring bags. That meant she still had to go through the bag-check line, but at least in the park, it was very light and gave her somewhere to put little things if necessary. We tried to make any permanent purchases toward the end of the day or sent them directly to our resort to avoid having to carry big blue WDW bags around the park.
I would say you really don't need a bag for a park map if you have a basic pocket in your shorts/jeans/whatever. Frankly, the current folding paper park maps have the "picture" of the park so irritatingly small that it's virtually useless. We still get one, just in case, but if we find ourselves in need of a map, we'll look on the
MDE app, which has a GPS feature to let you know where exactly you are and what you're near. With that in mind, one thing that hasn't been mentioned as a potential bag/pocket essential is one of those little portable phone chargers that looks like a lipstick case or a deck of cards (whatever size you get). After MDE kills the battery of my phone, these little beauties have been quite helpful.
