now i get you. US Military Base. and the girls are USAG registered athletes. okay, then. if the kids have never competed before in a USAG sanctioned event, then yes, they must "enter" the USAG competitive stream by starting at Level 4.
if the kids have skills at a higher level, and have never competed in a USAG sanctioned competition and had not entered the stream as "old level 5", then those kids must also compete and enter at Level 4 if you want the kids to have what you are calling "credentials" to show their mobility. you can not bypass the compulsory system and just enter optionals or Excel. no can do. no matter where you live, and if the kids are USAG registered athletes, they MUST enter the USAG competitive stream in the new Level 4. from there they receive their mobility scores.
and if they enter as "foreign" athletes, and i can't see how they can do that, and then come back to the States, regardless of what level they competed as as foreign athletes, they will STILL have to enter the USAG competitive stream as Level 4's. so no, THAT won't be the most beneficial to the girls. you really ought to let your Coach handle this stuff so that you don't muck it up with the Host gym in Hawaii. honestly, you will aggravate them and they will end up telling you to have the Coach contact them.
there is no "procedure to figure out". the coach will enter the kids where they must be entered based on whether they have competed in a USAG sanctioned competition before, or not. unless you are a coach and a registered Professional Member, you have no say in the matter. i don't mean that disrespectfully, it only means that there is nothing you can do, or decisions that you may make, if you are not a USAG registered Professional Member.
finally, the rules are a bit different if you are a foreign athlete competing FIG and move to the States. that's a whole other can of worms, suffice, if Mustafina moved here and was allowed to represent the USA and was released by Russia and approved by the IOC and FIG, she would not have to enter Level 4 as a first time registered USAG athlete.