Missionary Time Capsule Idea -- I would do this just before they leave. Favorite place to eat, favorite music/song, favorite movie, etc. It would be fun to have them open it up after 18 months or 2 years.
Farewell cake for a Sister Missionary. The fondant beads are Young Women's Values colors and the inscription on the side reads: Mis-sion-ary: Noun: Someone who leaves family for a short time so that others can be with theirs for eternity.