if they are still seedlings they will need to be a bit bigger before you plant them out. A small plant about 6" tall is ideal. I do have many penstemons in partial shade and the are happy.
Also they will need to be hardened off before going outside permanently.
When they get about 4" tall pinch out the growing tip so they start to bush out.

Thanks very much Seaburngirl. They are about 4" now, and although I knew about the hardening off, I wasn't sure about the pinching . . . I've been 'pinching' my Hibiscus trionum and Nepeta fassenii seedlings, but with doubt in my mind! Good news that yours are happy in partial shade, so I'll go ahead in a few weeks time.

All advice much appreciated.