It's moving day! After the seedlings have a few sets of secondary leaves, they should have enough of a root system to hold together the cel-pack root ball. I just watered my seedlings yesterday with diluted fertilizer from bottom-up, so I was pretty confident that the soil would stick. I used a razor blade to carefully cut away the cel-pack, as to not damage this little guy.
I then put together a well-drained soil mixture, consisting of:
This last photo is intentionally out of focus to show the soil mixture, rather than the seed leaves.