Is it permissible to perform Hajj on behalf of one's father with a grant from a company, knowing that the employee is able to perform Hajj with his own money, and is unaware of the extent to which the source of the grant money is lawful?

It is permissible to perform Hajj on behalf of one's father if the entity donating the Hajj expenses does not object, because its wealth is mixed and dealing with mixed wealth is permissible. However, performing Hajj at one's own expense is better.