If you choose to file yourself, you'll get no child tax credits (Refundable CTCs are limited to 15% of earned income excluding the first $3000). However, if you choose to file jointly with your spouse, based on his income, you should get $3000 per year refunded to you (For 2009 and 2010 if you didn't file yet, you'd get $3800 due to the MWP credits).
You'd need to obtain an ITIN number for your husband though. This would be done on a W-7 form at the same time as filing the tax return. He'll need to provide his passport either to the IRS or to a Certifying Acceptance Agent in order to do the W-7 procedure.
You'd need to make an election to have your husband treated as US tax resident; you can revoke this at any time, but can never make it again, so you can't dip in and dip out as convenient. Since he's paying UK tax, the Foreign Tax Credits would avoid any US tax, and you'd remain with the refund.
You can back file back to 2008 if you haven't already, meaning possibly over $13500 refunded to you now!
