I have one 13 yr old cat who cannot eat grains.  He breaks out around his mouth, under his chin and up the face into the areas of his ears.  He had an allergic reaction (vomiting and diarrhea) to a ground corn litter.
But eliminating corn did not completely clear up his face.  He is doing well on grain free dry food that is expensive because I have to get it from the internet stores. 
The 16 yr old cat is on medication for congestive heart failure and he requires weekly IV infusions for renal failure and of course, he is on the r-d food (also dry and expensive) from the vet.
I have never fed my cats canned food as I thought it would be higher in carbs and bad for their teeth.
I add water to the bowls of the dry foods so that they get adequate intake. 
I was feeding them organic foods (also dry) but cannot get organic special foods and I figure they would be astronomical in price.
My question is, can I feed them canned food and meet their special needs?

Venus, check out some of the other threads posted here about food: espcially Prepared food… wet vs dry?, and Wellness. I learned a lot.

Wet food is much lower in carbs than dry, and is less of a problem for teeth than I always thought. I used to feed exclusively dry and give them a rare canned treat, but I’ve been adding in more and more wet food since I’ve become better informed. It’s still a process, slowly switching them over bit by bit. You’ll still have to read the labels on the premium food cans, just make sure you know which grains your cats have the allergies to. Some use rice instead of wheat or corn, and then there’s the completely grain-free ones, which might still have potatoes or sweet potatoes instead.

Our resident vet Dr Gaspar makes a few recommendations on wet and dry foods in the other links, but I’d still check with the vet you’re seeing now since he/she knows more of the details on each of your cat’s conditions. I don’t know where you live, but you can use the internet to find retailers in your area, then just stop in all the pet stores you see to see who carries the brands you need. It took me a looong time to find local sources, but I finally managed to find some, so now there’s no ship charges! *does happy dance* : ) BTW, just got an email from petco that they’re now carrying wellness, so that maight make things easier for you.