The final logo should be stylized rather than realistic with a modern, but timeless feel. It should also have the capacity to be reproduced in a single color and still be clearly read from a distance.
The idea I have at this time for this logo would be a man and a woman in silhouette(?) on either side of a young tree with blossoms, working and nourishing its roots. Both the man and the woman are in a kneeling, almost prostrate position. The tree may be a-symmetrical, but the positions of the man and woman should be symmetrical on either side of the tree, though they don't have to be doing the same things with their hands. Other elements may be included to create a-symmetry, though those elements are not necessary for the concept. Some of the branches of the tree create an intertwining K and I, which may be in an alternate color from the tree, but still needs to be clearly distinguishable when reproduced in a single color. I would hope this would give you some ideas to create something you find inspiring. Feel free to adapt this concept into something that truly inspires you and others.
I would be open to other concepts that are in keeping with the metaphor and core values of the marriage and that meet the other design parameters of the project.
Please, nothing with carved initials. We think of our marriage as something more organic than as something we impose on each other or on the world.