you sound like you’ve an excellent vet 🙂 familiar with the struggles of seperate feeding schedules.. I had indoor only cats on wet food and another allergic to wet food so could only have dry and our only optinion was seperate room feeding.. if our kitten and 2 1/2 cat can eat the same food that will make it a little easier but I understand kitten will still be on a kitten food diet for a while yet…
as for your older fur baby it’s extremely important to keep on the strict diet that’s been perscribed so looks like you’ve no option but to feed in seperate rooms and brave the early morning 🙁
as for treats I used to buy treats but not anymore .. now I give them all a raw fresh chicken wing as a treat believe me dry treats don’t have a patch on the raw chicken wings and it will be same for your older one with kidney issues as raw diet is get for kidney health.. I only give dry anti hairball treats in the summer when they are moulting and that’s only because they are indoor only and don’t have access to grass