Is it ok to mix pre-made raw and canned food?

My healthy almost-17 year old spayed female cats have been on a regime of diluted Wellness and By Nature Organics canned food (for extra water content) during the day and Wysong Uretic kibble at night. I just switched my 8 month old Pom/Chi to Paw Naturaw organic pre-made raw food and she just ate part of a thawed chicken patty last night and did great. She switched cold turkey from a homemade cooked chicken and veggie diet without a hitch. I tried the food on them today to see if they would eat it before I ordered them their own bag of the formula for cats and I had to make a half and half mix of Paw Naturaw and canned food to get them to eat it. I'm confidant I can get them to just eat it straight eventually since I had to work harder than that to get them to eat canned food originally. When their own bag gets here I plan to use the paw naturaw to replace their canned food-they still need the Wysong since one cannot go without it without getting UTIs. I know I can't feed kibble and raw at the same time, but is canned and raw ok? And how long after their last raw meal of the day will it be ok to give them their kibble?.