Pilots Wife,
I'm with the group that say you guys should take the offer. There are no guarantees out there for certain, and someone already mentioned Comair.
Ask yourselves if you stay where you're at where you'll be in 15 years if everything goes well at your current airline. Now, ask yourselves the same question with regard to where you think you'll be in 15 years if he takes the United offer.
Again, no one can guarantee what will happen with the airline, the economy, etc. But being on the front of the wave of hiring should provide a significant advantage to taking the legacy option. Timing is everything.
Take care,
Lee