I'm no expert but if you are taking your kids you should not do a garentee becouse you could be vary far apart. We have sailed with our 4 kids 3 times, just like you, we did the balcony and put the kids in a quad across the hall. IMHO a cat 11 is not worth the extra money. These cabins are not that much bigger and you really do not get any REAL perks for a suite with Carnival.. I perfer to book the lowest level Balcony becouse other than suites all the rooms are the same, You only are higher up and and since Destiny class are split higher up does not matter.
Your price is not to bad but imho you could save a lot of money going to a standerd balcony and you won't be dissapointed.