Completely switching food and feeding times.

I have 3 cats who have access to dry food for most of the day so they can graze as they please. My 8 year old cat is morbidly obese and I took him to the vet for chronic vomiting. They say he is in good shape except for likely pancreatitis and his blood sugar is on the high end of normal. Vet recommend pepcid 2x a day for a while and to switch to a good wet food and get his weight down. He also had lipidosis about 3 years ago(he got stressed when I moved and wouldnt eat). After he recovered he gained a ton of weight. My other two cats, 4 years and 15 years, are very healthy with no weight issues.
The 15 year old meows and freaks out if he can see the bottom on the food bowl, and my 4 year old was found by someone at my job when he was a day old and I bottle fed him and he wouldnt even touch the wet food during the weaning process, just went straight for the dry food. I am concerned that none of them are going to want the wet food, but I will bring a few good types home and see how they react to any of it. I am also concerned the 15 year old will become stressed that he cannot access his food all day anymore. He only eats like 3 pieces at a time so I feel like he wouldnt eat enough if I only gave it to him 3x a day.
Does anyone have any suggestions on how to go about this transition? I could continue feeding dry to my other two cats but I dont know how I would keep my fat cat away from it. Is it best to change all three of their diets to the wet food? What do I do if they wont eat it? Thanks for any help!

Try some of these tips. Because you have both a senior and a cat with a history of obesity and fatty liver you need to transition very slowly. Try giving wet food for just one meal and see if you can a least increase their water intake and then you can slowly reduce the kibble. It's okay to feed multiple times a day, too. my 14 year old eats like 6 times a day, because he's a grazer and my other cats will go for his food so I have to feed him several times. Try using some toppers to get them to eat wet food. Freeze dried meat treats are going to be your best friend during this time.

http://catinfo.org/docs/TipsForTransitioning1-14-11.pdf

Thanks that was helpful!
I tried giving a couple samples of high quality grain free wet tonight to see how they would react and slowly introduce it. The fat cat and the senior cat were very interested. My bottle fed cat wouldnt even go near it. He actually wont even be interested in lunchmeat, fish or anything but will pester me if im eating cookies, french fries etc. So I figured it would be an issue with him. I put him in a different room with a portion of dry to see how much he would eat at one time. Not sure what to do about that yet.

Here's an article that specifically addresses transitioning from free feeding to scheduled meal times:  http://www.thecatsite.com/a/transitioning-free-fed-kibble-kitties-to-timed-meals