Asking for the 1600 loop is probably your best bet. 1600 shares two comfort stations; one with the 1500 loop and one with the 1800 loop.
If you click on my Fort Wilderness page in my signature, I have a FW map on my page so you can see the basic lay out and CS locations. Just make sure your reservation is marked to put you close to a CS.
Just for clarity, the designated pet loops are the full hook up 800, 1600, 1700, 1800, & 1900 loops or the 300 or 700 "preferred" loops. The 500 loop is an overflow preferred pet loop when additional pet sites are needed. Three "pet walk" areas include a canal pet walk off the 1800 loop, a canal pet walk off the 300 loop and a nice wooded walk behind the 700 & 800 loops.
Now for the dachshund. Technically, you are not allowed to leave a pet in a tent or pop up unattended. But, I would be lying if I said Ntasha had never been left alone in the pop up. You have to decide what you are comfortable with. While I wouldn't think "escape" is a possibility for your dachshund, barking might be.
Should you decide to try it out, Fort Wilderness has an on site kennel for your standard house pets. The kennel does NOT accept reservations at all, so don't bother trying. Current 2004 rates are $6 for a day stay and $9 for overnight. If you check in for the week you will pay the overnight rate. You must drive them to the kennel, you can NOT walk them to the kennel, nor can you walk you pets out of the pet loops themselves.
The FW kennel asks that you stop by to walk them twice a day yourself, but you can pay an additional $2.50 (each walk) for the FW employees to take them out.
Most of the prnd/cases are stacking models, one over the other. Interior dividers can be removed to allow space for larger dogs. In addition to these cages which are indoors, they still have a number (I'd say 15 or 20) of outdoor cages/runs. While they have ceiling fans over them it does get quite warm during the summer.
The kennel is open from 7:30AM to 10:00PM, but if you are out late the staff at the reception outpost can walk over to the kennel to get you dog to allow them to come to the site for the night.