Is it permissible to give charity equivalent to the value of two camels instead of sacrificing them as my father requested, and if there is another way of giving charity that would be more beneficial for him after his death, knowing that the money paid is from my own funds?

Fulfilling the covenant and will of one's parents after their death is a part of perfecting one's dutifulness to them. If the will does not pertain to the parent's private wealth, then its execution is recommended but not obligatory.

If you wish to execute the will from your own private wealth, you can direct it towards an ongoing charity (Sadaqah (definition) Jariyah) such as building a mosque or a school, providing water, or distributing it to the poor and needy. Ongoing charity is better than intermittent charity because of the continuity of its reward after death.