I have to actually wait until the DVD player boots up, and then
go into the device and manually switch it, which isn't
a big deal, but thought maybe someone here knows a trick.
You don't have to go into the device; you can have the input command in the activity.
I have a sort of reverse of the situation: the DVD recorder won't change its sources until it's booted up, so I forget about setting the source automatically and have a "source" button in its activities.