Thank you for the update on the 'buss.' Too bad the kids played with it; I have seen some wonderful pieces turned into 'pieces' by children playing with grandpa's old gun. To answer your question, there are folks on this site who do wonderful restoration on old arms.
First, did it have a bayonet? Condition from breech back to butt appears to be quite good, so do not clean, wax or do anything else to it.
The forearm can be easily restored with having missing wood added in and colored to match. The gun can be returned to flintlock or not as you wish. Correct parts are available and match in quite well, by a skilled restorer. Be sure that no metal is cleaned or otherwise changed. Patina is everything in America, not so much in Europe. but you have an abundance of it and it will solidify the upper value of this gun. You will have to spend some money to get a top notch restoration done, but in the long run should be worth it. Good luck!
Dick