It would probably behoove you to get as much information as possible about each autograph from your mother to establish provenance. Such as any little particulars about how she actually obtained the signature.
It might also be in your best interest to have the signatures authenticated. There are companies that specialize in authenticating signatures that are recognized as experts in such things. Their authentication can add much to the value when brought to auction.
Autographs are very highly prized by collectors.