I'm assuming your equipment is new to you, since you are asking us here how well it will work. The answer is to take it out before you get to Bosque, and find out for yourself. Your 400/4 with teleconverters is long enough for Bosque, especially if you are using a camera with cropping factor--As with most wildlife shoots, there will always be instances where you can use a longer lens, though. You don't explicitly mention a 1.4x teleconverter, I'd be sure to have one there. Don't forget lesser focal lengths as well, including wide angle.
There are lots of web guides to how to get around at Bosque. Michael has a page on it on this site, if I recall. In short, be sure you are there for at least thirty minutes before Sunrise for the morning blastoffs, stay till you get tired of it, and be there at least an hour before Sunset when the birds return. If you aren't sure where to go, go where the crowd of cars is. In one of Michael's old LL DVDs, he has a pretty good video report on Bosque, now that I think of it.
There are lots of chain hotels in Socorro, choose the chain that fits your budget and desired comfort level. I usually stay at the Motel 6, but I don't have a wife to keep happy! Make sure to take the family out for green chile cheeseburgers at the Owl Cafe at least once.
If the family wants a break from continual bird viewing, consider driving over to the VLA radio telescope for an afternoon, especially if anyone has a science or geeky bent.
