4-5 week old foster kittens have started suckling on blankets... Need advice

I am fostering a small litter of three kittens. For some background, they came to me emaciated and suffering some pretty serious diarrhea. I'm currently feeding them a mixture of KMR, critical care kitten food and pedialyte mixed up in a bowl. They are doing much much better and the diarrhea has almost abated.

Today I let them out of their playpen to romp around the living room and they came across my dog's fleece blanket. They immediately started trying to suckle the blanket. I know that this behavior is caused by them being separated from their mother too early. What I really want to prevent is this behavior persisting into adulthood where it can become quite destructive. I've read that feeding them a high-fiber diet can help but they are already eating some pumpkin to help with the diarrhea.

I was wondering if it might be a good idea to bottle feed them once or twice a day would help satiate their need to suckle. However, they are currently eating on their own and I don't want for them to "regress" and depend on bottle feeding. 

Any ideas, advice or thoughts?

Thanks in advance!

I wouldn't worry about it turning destructive, when they go for it give them extra attention and in the end they'll probably just end up "kneaders".

I am no expert here (except for 1 cat in this predicament) but I think for them to get comfort from food is worse than what they're doing now.

You could certainly bottle feed them a couple times a day since they are still so young - 4/5 weeks. It may help to soothe and calm them. That in addition to their regular diet will be just fine and will not make them regress. It may be comforting to them. Such sweeties and too young to be away from mom.

Do not worry about this behavior. I know of many kittens who have this habit and it always diminishes little by little as they get a little older. My cat, Presley, did this up until almost a year of age then stopped. It will cause them too much stress if you try to cease this behavior. Let them have the fleece blanket. Most kittens will find something else to suckle if you take away the fleece. Thanks for fostering !!! There is such a need.

Mine particularly like the new supersoft "sherpa" blankets, and even the old adults cannot help but make biscuits if they find themselves standing on one.  I sleep under one, which gets me lots of feline backrubs.  I agree with the above, the kittens will be fine, less likely to be problematic as adults if they can knead and suck to their heart's content.  Babies with mom cats even do this on a really nice soft blanket.