This is the same one that blew in 2004 when there was a limited impact on slights to and from Iceland and some transatlantics. This from Wikipedia:
A week-long eruption occurred at Grímsvötn starting on 28 December 1998, but no glacial burst occurred. In November 2004, another eruption of about one week began. Volcanic ash from the eruption fell as far away as mainland Europe and caused short-term disruption of airline traffic into Iceland, but again no glacial burst followed the eruption
Don't want to be complacent but assuming its the same as then, the impact ought to be pretty minimal.