Yes, the North American rat snakes were separated from the Elaphe, and assigned to Pantherophis.
The corn/king hybrids are indeed across Genus boundaries, as kingsnakes are in Lampropeltis. It was quite a surprise. Reptiles don't seem to care as much about our taxonomic classifications as we do.

Burmball (Python X Python--same genus)
http://www.johnberryreptiles.com/images/Burmball_3.JPG

Wall (ball/woma cross) Python X Aspidites -- Different genus
http://www.spitfirereptiles.com/sphp...4-0901.med.jpg

Carpall (Carpet/Ball cross) Python X Morelia -- Different genus
http://www.fororeptiles.org/galerias...1_Carpall_.jpg

So, intergeneric hybrids don't appear to be very far-fetched at all, in snakes.

However, from what I've read, someone has attempted to cross a spotted python with a ball python, and got locks, but there's nothing reported anywhere on any babies produced, yet. So, that's discouraging for the success of a Children's X Ball cross. Antaresia might not be compatible with Python.