Hello, I guess regardless you will use that hard maple because you have set it aside, it is nice and seasoned, maple is resistant to denting, at least tangentially to the growth axis, it is easily obtainable and probably where you are maple is commonly used for this purpose.
Here in this area maple is not a common choice for a mallet, beech is, for many of the same reasons.
The mallet I have been using for some years now is a piece of ash stem with a branch coming off of it at a more or less 90° I have cut to form the grip. This leaves an extended amount of continuous grain and is very strong. It took some getting used to the asymmetrical weight of the thing because its form is organic and not contrived. Also, I have a nice solid mallet from hornbeam, (Carpinus betulus), I picked up from a guy in Krakow, Pl.
Some other woods good for mallets are, black elder and birch root. The wood from the root of many trees would make excellent hammers as long as they were solid and not laminated. I always try and salvage root wood if I can manage it.