Sounds like a challenge!
I have a daughter whose husband “farmer” Plants and nothing grows to maturity...no weeding and expecting sprinkler system to do the watering is a near total loss each time...but he tries again something different...Lettuce was good though!
Corn stalks were just enough for fall decorating. No ears over 1 inch around. Potatoes and other things eaten by bugs.
I took over care of the tomato plants ( in Pots) one summer when I visited, and watered and fertilized etc, until we had more than we could eat. The few jars that I canned sat on the shelf to decorate the pantry until after Christmas when she decided to use them.
I have one tomato plant here in Florida this year...First flowers were eaten overnight so now the next ones are small tomatoes, getting the dish detergent treatment, and it seems to be working...flowers I have everywhere!
Hubby usually has pretty good luck with most of his crops. He is still eating corn on the cob that we froze straight from the garden into the freezer.
I still have a few frozen tomatoes from last year that I add to soup or chili. Made one batch of salsa - he said it was too hot. I just mix it with sour cream, and I think it’s just right.
We don’t have any squash, zukes, or cukes yet. It’s always a toss up on those. He like to stir fry the crook necks. I make spicy pickle spears out of the zukes, and dill pickles with the cukes.
I haven’t checked the corn yet. He said tomatoes this year didn’t turn out - he used jiffy mix starter, and I told him it wouldn’t work very well, but he ignored the warning. LOL
Consider giving him a present of a book the next time you go visit there : "Square foot Gardening" by Mel Bartholomew.
Mel's program is designed to start small to encourage success, it teaches improving the soil , mulching to minimize weeds and retain soil moisture, pest control,
companion planting,benefits of 'raised bed gardening,etc., and proportions plants per square foot, recommends of different varieties of vegetables, etc., an is easy reading.
Everything a beginning gardener wants to know to be successful, .. and then you build on your successes. Highly recommended !