I went back on the website, as I was checking the offer was still there, the "chat assistant" came on. I asked with them, and they confirmed the offer was "plus"
We're not booking though, as on the French site, they've 45% off with under 12 free, which comes out at roughly £600 cheaper. This also works better for us as I've 2 children who prefer eating smaller meals, so the free full board may work out too much food for them. Now if it was just me and hubby, it would be perfect