Unless you have some idea of the password or it is a short password, you have little chance of recovering the coins.
The best bet is to examine the CDROM very carefully as has been suggested and check with your mother if possible, what passwords he may have used for other things such as email. There may be a pattern. If there is any paperwork, check that for passwords too.

I would not suggest you hand your wallet out as it is not corrupt and could have a simple password that others with powerful equipment may hack in minutes.
What is safe, is to make a 'hash string' using this btc2john software.  https://github.com/openwall/john/blob/bleeding-jumbo/doc/README.bitcoin It looks daunting but isn't. the result, which will look something like this:  $bitcoin$64$02eecf1f942b9c8cf7479a9a5f1055297fed799cac5a79c4635973c83cb6b938$16$15863bcede2eb336$343753$2$00$2$00 can safely be sent out to people. If that can be decrypted correctly, the password used is correct.  That string,does not contain the key with the funds, that are in the wallet..