Buddyboo, all I can say is to ask. Let them know everything that you stated here and see what they say. Sometimes there are hard and fast rules, and other times there are rules that are basically guidelines that may be shifted a bit. The kids' club in question can definitely let you know how they handle a situation like yours.
Also, don't forget that you can have a private in-room sitter. We have gone that route and all the sitters that Disney set up for us were wonderful. From the official WDW website:
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Name: Baby-Sitting performed by Kid's Nite Out
Description: For private or group baby-sitting, call (407) 827-5444.
Information: (407) 827-5444.
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