Zantedeschia aethiopica 'Crowborough' arum lily - Unusual, pure white hood-shaped flowers that are up to 10-15cm (4-6in) long are produced from late spring to mid-summer. It makes a striking architectural clump with lovely arrow-shaped, glossy dark green leaves. It looks great grown beside water as a marginal plant and can be left outside in most frost-prone areas if it is given a deep winter mulch.
What if a few single stem cala lilies lined the path to where I propose? Either on the ground in mason jars (or something) or attached to a tree/bush somehow? One could also be at the turn off from the street so I know where to go! :)