Thanks for the advice.

We have gone ahead and purchased open coupons for US Airways via Charlotte and United via IAD.

From viewing Flyzed the loadings are looking good for US Airways (hoping it stays that way).

We are hoping to make the 7.20am flight if our flight happens to get in early (fairly common) and can get an easy run through immigration.
We have upgradable to first status to LAX which will help with retreival of luggage and hitting immigration ahead of the rest of the PAX.

If we dont it is no biggie.