If you like crafts projects you could make him a lovely celebratory necklace from little mice teeth.
If you really want to impress him, you could also boil and bleach the bones to add into the necklace for a festive kind of “witch doctor” look.
Of course you’ll have to take a little sojourn out to mousey cemetery with a trowel….
But hey I’m not the one who decided to prematurely bury them all, now am I ?
I can just hear him singing now:
oo ee oo ah ah
ting tang wallah wallah bing bang
Oo ee oo ah ah
Ting tang wallah wallah bang bang
:D