Nial made sure that his father moved to the Orion shelter since it was the most secure there. The defensive mechanism were beyond the comprehension level of the origin humans and there was also Erio, the guardian of the Orion shelter.
Other than his father, Nial didn't really bother telling anyone that they had to move to the Orion shelter since he offered them a choice to move in if they wanted. He was not going to force anyone and he would accept their decision regardless. It was not really difficult moving from one place to another, either way.
Teleporting to the Forest of Life and back was pretty simple since it cost only a few Origin crystals to empower the teleportation circles.
There was no need to force anyone to come over for the time being, especially since Nial had nobody else in the Halheim shelter whom he wanted to have in the Orion shelter as much as his father.