FamilySearch.org Family Tree recently added the capability to share Temple reservations with family and friends directly. There is now a Share link under the Temple menu item that appears for those who are members of The Church of Jesus Christ of Latter-day Saints and registered on FamilySearch.org with an LDS Account.
On your reservation list, there is a check box next to each reservation which allows you to mark the reservations you want to share. Marking this box enables you to send the reservations to a family member or friend by email. The reservations are then marked with an share envelope icon and sent. When accepted, the reservations will disappear from your list. If your invitation is not accepted within two weeks, the share envelope icon will be removed, allowing you to print, share, or unreserve your ancestor reservation again.
This is a major step in avoiding lost cards and misunderstandings. You will still need to monitor whether or not the accepted reservations are used to perform the ordinances.