Thanks for those very helpful posts, everyone.
Donna D., that sticky thread on the Casita forum was also enlightening about the dangers of getting it wrong.
We're going to go with a 30 amp connection. As well as handling our trailer without issues, it will enable RVers we know to come and "camp" in our driveway without tripping breakers or putting their appliances at risk.
Brent and Cheryl.