It's not allowed, since your wife does not qualify under FB2.
Look, at some point either NVC or USCIS is going to pull your A-File, and they'll see you're a citizen. At which point the whole thing is going to get messed up and you'll need to file the I-130s for your children. So why not do it proactively once you get the oath done?
There's also a karma issue here. Your wife and children have been waiting so long because FB2 is hideously oversubscribed. And now you're going to be taking three additional visa numbers out of the FB2 quota for your family, instead of having them taken out of the unlimited IR pool. That might mean that someone else gets an interview and a GC, or it might mean that someone else gets to file an I-485 before their non-immigrant status runs out. It might delay you a little bit and cost you some money, but you'll be a doing a good deed for someone else.