They always asked us to remove things from the stroller. It was years ago, but I still see people unpacking the stroller. We miss our pack-mule - I mean, stroller

You will have to remove things from the stroller to get on transportation as well, so packing as light as possible is a good plan. If you will return to the resort for a break during the day, then you can save some of your stuff for later and not carry it all now
These are the things I have done to down-size my family's stuff since we don't have a stroller to haul it all: small camera only for personal shots (I don't need a photo of everything and if I did then I would spend too much time snapping and not enough enjoying - YMMV), filtering water bottles so we can refill in the park and carry less, all-natural sunscreen so we can all share one, no misting fan - it doesn't help much in the humidity anyway but buying a frozen lemonade and sitting in the shade to cool-off does, no extra clothes - no wet rides unless we are happy being wet or going back to the room soon, jackets or layers worn around people's waist rather than all carried together, calorie dense snacks so that we carry less weight and volume of snacks, even when kids were small they had a small waist pack with their own snacks.
The first few times we went with small children, we had everything we might need - unloading and reloading the stroller was misery! We decided that we didn't need everything possible since we were in WDW and could buy almost everything we might need - so only carried what we knew we would need.
Obviously what worked for us may not work for you, but we found that we didn't have to carry as much because: we were returning to the resort anyway, we were going to buy the fun Disney snack anyway, and Mom didn't have to carry everything or organize it all. Because I did not keep track of it all, we (child) did lose (left in restroom and disappeared) one clothing item total during our more than once a year trip since our two children were 3mo.s and 2 yr.s I did not like losing the layer, but if that's all we ever lost during more than a dozen trips where I didn't have to carry and organize it all - the trade-off was worth it. That's my mom-to-mom advice FWIW.