I am buying a better digital piano to replace my YDP-223, which will go to my parents home. I have two options:

A. Buy a brand new, in-the-box, CLP-280 NOW for $3K + tax and delivery.

B. Wait for a few weeks and get a new CLP-380 for $5K (or less?) + tax and delivery.

The new digital will be used as a backup piano by my kids. When one kid is already using the grand, the other kid can play the digital and doesn't have to wait. (We don't need the head phone feature as the digital will be in a separate room at the other end of the house.)

Would you go with A or B above?

I know I sound like a broken record, but only you can answer that question. The 380 is a newer model with more/newer/better features. Is the $2k differential "worth it", well that's completely up to you. We use two digitals in much the same way as you're planning, a relatively new one and a much older one (~10/12 years). While the newer digital is quite obviously better in both touch and tone, I personally have no problems with the kids using the older digital esp. since it's primarily used for scales/sight reading. Plus having them work on three different pianos (with varying actions and sound) is perfect for getting them used to dealing with different pianos (e.g. recitals, competitions, etc).

If you're asking to assuage your fears, then I don't think getting the 280 is going to be the root cause for your kids not getting into Curtis (esp if you spend the $2k difference on enhancing other aspects of their musical development). However if you are focused on getting just that much closer to your acoustic, and your budget can deal with it, get the 380.