Should I try to reroute?

Money mostly

and probably plenty of it at this late date.

Icelandair won't offer you any special options unless or until they actually cancel your flight. Your ticket should specify the exchange rules tied to your fare. Most leisure travelers choose fares that are not refundable and changes (if allowed) come with fees.

My son and daughter in law left for Scotland yesterday via Icelandair. They changed planes there and flew on. On the way back they have a 4 day layover in Iceland. I say go for it. Worse to get stranded at home than stranded there!

Have a great trip!

I assume you are worried about the possibility of a volcanic eruption in Iceland.

Most airlines fly a "great circle" route from the US to Europe. I've looked down at Iceland on flights from northern Europe (Frankfurt or Munich) to the US, so I'm not sure that flying a different airline will eliminate your concerns.

Try not to worry. My husband and our 10 year old just did their online check-in for their trip to Iceland tomorrow, with Icelandair. We've been following the news updates here:

http://en.vedur.is/about-imo/news/2014

Our other kid and I are going to Disney World tomorrow during hurricane season. Half the fun of travel is the not knowing what's going to happen, er, well, it adds to the excitement, anyway.
Have a super trip!

Airlines sort of fly a great circle route since that's the shortest distance. However, the world is not perfect and they actually fly the shortest time route which is dependent upon wind patterns. The eastbound track generally does not follow the westbound track due to varying speeds and directions of winds aloft. Time is gas and gas is money.

Generally, a slight ash cloud is not sufficiently thick to bar either a visual or at least an instrument approach and landing. The problem is the grit which eats the turbine blades alive and air carriers are not equipped with an eaps system. Motors cost more than gas.

Were it a direct flight rather than a stopover, they could just load on more fuel and bypass the mess, if it comes to exist.

Thus, your rerouting option would be to go to another carrier that doesn't make the Iceland stop.

It will surely cost you beaucoup bucks to change your flight this late, and from what Martha posted a few hours ago there seems to be no eruption or flight disruption. I suggest going ahead with your Sunday flight, two days in Iceland, and on to Munich. No one can be sure, but it seems like the odds of either eastbound Icelandair flight being cancelled are pretty small.

FWIW, we flew to Europe twice on Icelandair in recent years. In 2010, an eruption closed down most European air traffic for a week or two, and Iceland stayed closed after mainland Europe reopened. Icelandair put us on a nonstop Air France from Paris to Seattle and we landed about an hour earlier than we would have otherwise. In 2011, an eruption closed Reykjavik for a few days, including the day of our flights home. Icelandair put us on three flights home via London and Vancouver. We landed in Seattle a few hours later than planned. They took great care of us, and presumably their other passengers, under very difficult conditions.

So I'd suggest going ahead with your plans and being willing to roll with the uncertainties. You won't be left hanging unless everyone else is too. And, since we're not flying to Europe this year, the data suggests that there won't be an eruption! ;)