I vote for the kids. I try to get my wife to clean her own guns, but I do not like the way she does it so I do it myself.
This is some info I previously post on ultrasonic cleaning:
I have used ultrasonic cleaners for many years, but not for cleaning guns.
What I would do - would be to put water in the ultrasonic tank, and then put the cleaning solution in a smaller container that would hold the part to be cleaned. I actually used a glass beaker, but anything that will transfer the ultrasonic energy will work - you can see the bubbles in the inner container. This is beneficial for 2 reasons, one it is easy to dump the cleaning liquid, and secondly the dirty cleaning solution is not in the ultrasonic tank.
Keep in mind that extended ultrasonics can cause premature failure of materials, due to the propagation of stress cracks.
As a caution - I would be very very careful what I put in an ultrasonic tank, and how long I would leave it there. If used properly the ultrasonic tank or vapor degreasor is an excellent tool. BUT an ultrasonic cleaner can cause microcracks or cause existing microcracks to worsen. Putting a barrel in there (suspended, not on the bottom) for a short time should probably not cause any problems. I would be very very careful about using it on any polymers or parts under stress. Microcracks are not visible to the naked eye but only under high magnification. I have seen many things damaged by improper use of ultrasonics.
Just for clarification on the ultrasonic tank cleaning: I have never put any gun components in an ultrasonic tank, but I have used ultrasonic tank cleaners, and vapor degreasers with ultrasonic tanks. After looking at different types of failures under high magnification 400x-10,000x I can tell you that ultrasonics can cause microcracks in materials and can also worsen existing microcracks. Ultrasonics can also cause loosing of fasteners such as screws, nuts, bolts, and pins.
These microcracks will probably not be evident to the naked eye, especially after only a couple of cleanings. These microcracks could over time lead to failure of components. Firearm components are subject to a lot of stress, and I would be concerned over time if I consistently used an ultrasonic cleaner. The barrel is probably thick enough not to be functionally damaged by the ultrasonics.
That said, if you wanted to put the polymer parts in an ultrasonic tank for a couple of minutes to loosen up any gunk on there, I would not worry too much about that, but I would not leave it in there for more than that.
Also if you do ultrasonic any items that have any fasteners, I would recheck them.