This will probably be the last year we stay in a 2 bedroom. You have a few options; borrowing like some others have suggested, go less days, stay at a resort where points cost are less, use smaller accommodations or add-on. We will probably use a combination of all of these with the exception of add-on for the foreseeable future!
Another option is to spend a little bit on a transfer. For example, if you are 10 points short, you could try to arrange a transfer of 100 points from another member. Use those points in your next vacation and bank your own points into the next year. As long as you pay attention to how your trips are booked and always use your banked points first, you should be able to cover 10 years of the points difference. Definitely a lot cheaper than adding on!