Yep, I do that too,
setting the plants down and 'getting around to' planting later . . . learned the hard way to set 'em in the shade where the sprinkler will hit them. If they do get hot and dried out, set them in a bucket or pan of water until they're good and hydrated again before you plant. Potting soil bakes hard as a brick and is sometimes hard to get wetted through again unless given time to soak up.
Good choices on the purslane and lantana. Both stand lots of sun once they are established.