don't waste time and tree grafting onto seashore.
there might be benefit from approach graft, maintaining the original trees root system. has been done with some success.
I read Whitman had his trees growing in large buried copper pots.
alkaline soil seems to be a problem for these trees, as are cold weather, high wind, low humidity, and salt.
order a tree from Hawaii. Already a slow to fruit tree, start as big as you can. Also, a larger tree should be more hardy, smaller trees are much more sensitive to the cold, etc.