Stuff it, I have just re-read the whole post..
Sounds like this old guy has totally lost his marbles & needs your help in redesigning his plot.
Art! that's what he needs, a work of art on his plot.
Its best to keep your plans for his plot a secret, don't want him to get too excited, so working at night is your best option, I also would recommend making this a gift, so no need for him to know that you have done all this hard work for him.
You need to consider your planting carefully, select the best quality products & attention to detail it vital, to help you I have found a garden that I feel will look appropriate for such a character, please see the pic below:
Please note the scale of the statues, these can vary in size if needed, but I think if done correctly, he will love the final effect.
Midnight gardening, you cannot beat it 😉