So our time in HI is coming to a close, wife who is active duty will have her new duty station in California. So we're planning on sending our firearms back home to family in MD. Currently I have a temporary (non-active duty) assignment on the east coast which would give me a great opportunity to fly back some of our firearms this trip.

Been here nearly 3 years and I never got around to getting that stupid clearance from HPD for the firearms. (I'm being treated for AHDH and sleep issues). But if they're just being checked and I'm cleared for possession (I have a CCW permit in FL with reciprocity) in the state(s) I will be arriving in... They should be able to travel as declared firearms in checked baggage right?

How many guns total are you needing to transport?  How many handguns?  Are any of them registered with the PD in any HI county?

The HI registration status of firearms are not an issue for flying with guns.  Declaring a firearm doesn't require any proof of ownership or registration.

Check MD laws.  I think "Assault Weapons" are banned there.  You may also have to transfer ownership of handguns to whomever you are entrusting them to.  Those transfers may require you register the transaction and pay a fee.

Nothing is simple when it comes to gun ownership in controlling states.