The first 1-2 weeks are not really impacting eating. After that you loose most of the taste and things taste like metallic wallpaper. Later on he will probably run into problems with eating orally as most of us have and rely on the PEG tube. Before that soft food, pasta scrambled eggs soups milkshakes etc are working well.
Regarding kidneys and chemo. Cisplatin has a number of side effect and kidney toxicity is one of them. You want to be aware of that, an alternative drug is carboplatin with does not have that problem (to the same extent).

M