Another opinion... Access 2007 and 2010 are about as similar as Access 2000 and 2003 so I would not expect migration problems.
Also if you migrate the frontend, you can continue using the same backend until any issues are worked out or everyone has the new version installed and/or don't have to worry about migrating data. Although I don't even know if the file format changed (same extension).
I guess my point is there is not a strong reason not to split first. Although if your deployment timing is right now, I'd do it Duane's way as there is a little more hassle in manipulating 2 files vs. 1. I'd also do it duane's way if migrating major revisions like 2.0 to 95-97 to 2000-2003 to 2007-2010. I mention that list for completeness... But if someone is out there not using at least 97: Yikes, upgrade.