I already have the written permission from their daughter.
You can find the information below in the FamilySearch Help Center to assist you:
Can I request proxy temple ordinances for a friend?
Article Id: 926
April 20, 2020
"When submitting names for proxy temple ordinances, members should generally submit only the names of persons to whom they are related" (General Handbook: Serving in The Church of Jesus Christ of Latter-day Saints, 184.108.40.206).
Before you can request proxy temple ordinances for a friend to whom you are unrelated, you must submit signed permission from a close living relative of your friend.
A close living relative is an undivorced spouse (the spouse to whom the individual was married at the time of death), an adult child, a parent, or sibling. Please see the Church’s General Handbook, 220.127.116.11.
Make sure that you have signed, written permission from one of your friend's close living relatives. We cannot accept signed, written permission from yourself or your deceased friend, it must be from the closest living relative. Word the written permission this way:
I, (name of person giving permission), give (your name) permission to do temple work in a Church of Jesus Christ of Latter-day Saints temple, for (name of deceased), who is my (relationship to person giving permission). (Signature of person giving permission)
If your deceased friend has no close living relatives that can provide written permission, then a request cannot be granted.
How do I add an unconnected person to Family Tree?
What are ID numbers used for in Family Tree?
Individuals for whom I can request temple ordinances
I cannot find any close living relatives to grant permission for ordinances
Doing temple work for people not related to me