Is it obligatory to inform the family of the deceased that an 'Umrah will be performed on his behalf, or is that not necessary?

For the proxy umrah on behalf of a living person to be valid, it is a condition that the person be physically unable [to perform it], with no hope of recovery, and that they give permission for it. It is also a condition for the proxy to have already performed umrah for themselves. Therefore, if you performed umrah on behalf of your disabled friend without his permission, the umrah is not valid on his behalf. However, you will be rewarded for your good intention.