I have a smaller person's sea kayak, sub 16 ft, and have spent a day here and there in ones for smaller paddlers than my boat.
I am leaving aside the the dog because there should never be a dog in a closed cockpit craft to start with, which is what this conversation has focused on.
My standard kit for a long day paddle is up to two spare changes of clothing including a spare dry or semi-dry suit, lunch plus snacks, two dry bags of medical stuff, two spare water bladders, spare gloves, head cover, emergency tarp plus bivy, a variety of rescue stuff including VHF, GPS, lights and more that I am forgetting. What I load up includes the basics to be stuck somewhere overnight, and I still have room to add the tent, poles, sleeping bag, a couple of pots for overnights on purpose.
There is absolutely no need for a small person to be put into a big boat for carrying gear unless you start to talk extended trips that only a small percentage of paddlers ever undertake, or you have impractical demands like big stoves or chairs that won't break down.
Canoe Pack Liner
Full Size Sail Rig
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