I sort of agree with Becca. I think it's a 'damned if we do, damned if we don't' scenario for any U.S. president; if they stay away, they're insensitive isolationists, and if they show up, they're imperialist attention-seekers.
I'd say it's even worse for Obama, because whatever criticism he faces from abroad, the domestic crap-storm will be worse by at least a couple of orders of magnitude. If he goes, he's a money wasting, communist, elitist Europhile. If he doesn't, he's an inept coward.