I have seen Moderate low carb described in various way - 30-50g carbs a day ( which overlaps with some definitions of the ketogenic diet as being under 50g carbs a day), 50- 100g a day and as wide as 100-150g + carbs a day.
Perrsonally, for a diabetic person, I would see 50-100g carbs / day as moderate low carb but for a non diabetic person I think the parameters would be wider, so more like 75-150g / day which would equate to around 25-50g carbs per meal and less than 50% of the carbs “ normally” ingested by most of the population
I would suggest looking for meals / recipes that he likes, can cook, which fall into that kind of carb range and which can then be put together to make up a meal plan that he might want to try