The AC/DC thing for sure, but do they even make them that way anymore, e.g. with 5 or so tip styles all built in to one connector? Every universal I've seen in a store for the last 15 years has come with multiple tips that you have to remove to change polarity.
Most universals go from 3V-12V, none of those settings will hurt a 2600. Too low and it won't work, and 9v-12V will work just fine.
For childproofing, just plug it in to a cheap extension cord and run a few passes of duct tape around the whole thing![]()