Is it permissible for me to take the transfer fees and the money from my colleague and keep it for myself, in exchange for my wife delivering a similar amount to my colleague's family?

It appears there is no objection to charging fees designated for transferring money, as a wage for this service. This is because taking a wage for transferring money is permissible, and some scholars have explicitly stated the permissibility of the commission taken by a bank or other entity in exchange for the transfer.