For that money, I would spend a week in WDW, and then a week on the cruise in a category 4 or lower stateroom. (Assuming that you can take two weeks). Personally, I love luxury accomodations, but $11,500 for a stateroom seems really steep to me. I agree about any price for quality family time, but the category 3 is not the only option. I think you can have that same quality family time for half the price.
Of course, that is my opinion. Everyone gets to spend their money however they see fit. If you feel that the perks of being in a category 3 versus a category 4 are worth the extra cost, go for it and enjoy! I'd rather keep the difference and put it towards more quality family time.
Good Luck with your decision. I'm sure you will enjoy it no matter what you decide.