Are we allowed to bring in new kids into the team if some of our current kids cannot come to Worlds ?
Yes. There are some rules about drivers (see the Next Level game manual), but, in general, bring 'em all.
I think as long as they aren’t on the drive team, it should be fine.
Even if the new kids were in another team during the regular season …we could replace our current kids with them ?
This is for the vex iq next level worlds…obviously the current kids worked on the robot and qualified …but since they cannot come…new kids from a team that did not qualify could be put in the team ?
Rule G6 gets close to talking about this, but it’s not clear. The VEX IQ official Q&A did take up at least part of this issue in https://www.robotevents.com/VIQC/2018-2019/QA/56. I suggest you read G6 and the Q&A post carefully, and if you have any further questions ask them on the VEX IQ Official Q&A. Good luck.