Congratulations on your new 17A! We travel with one medium sized dog. For us we have a dog pillow she sleeps on. For us it typically is place, right under the rear bunk. For most part she is then out of the way.
We have a small cabinet that is dedicated to the dog, all food, treats, tie outs, drying off towels, everything is in this cabinet.
Not sure what the 17A has for a rear bumper, but on our HTT we have a square tube that stores the sewer hose, on the curbside I place a small kids plastic beach shovel in the bumper as a pooper scooper. Works quite well, much better than expected.
If you typically use electric sites especially as it cools off in the fall, pick up a small electric space heater. Ours is really small ceramic unit, with 2 speed fan, with two temperature elements options. During the day if we need it, it sites on the stove, at night we typically place it on the floor, in front of the stove. The gas furnace does keep the floor warmer though. Do not be surprised if the first time you fire up the furnace it stinks really badly for a ½ hour or more (this is normal to burn off manufacturing oils,etc).
Lastly do not store the trailer with the bunks wet, if you have to open it up and let it dry.
If it is raining on your first campout, it is a good time to read all the manuals, and become familiar with all the systems.