I've never been to CBR but have followed the threads relating to the resort as we'll be staying there in January, but before the slated construction time. If I recall correctly, they are in the process of or have already installed slides at a few of the "quiet" pools. Would it be possible for you to still stay at CBR even without the main pool? Are there any accommodations CBR is making, such as allowing you to use the main pool at another resort?
When my kids were five, they enjoyed a pool...didn't matter what the amenities were, just a pool. Although they have fun with water slides and different pool features, they now actually prefer the quiet pools for prolonged swimtimes because the main ones are usually crowded.
I guess I question if it's really worth paying the difference in price for a Deluxe resort if the pool is the only issue. I will warn you that the main pool at the Poly in the summer is usually crowded, and it's questionable if all that are there are resort guests. Now Beach Club, with access to its swim area might be worth the extra cost. OTOH, Blizzard Beach and Typhoon Lagoon have some awesome kiddie areas, too. And tickets to the water parks will still be cheaper than upgrading your room.
JMHO. Giving you a few other things to consider.