Ireland/Scotland/Germany 15 days

My husband and I traveling to Europe in July (12-27) for the first time. Our daughter is in the military stationed in Germany, so we will definitely be spending some time in Germany (SW of Frankfurt). Plus we got the best airfare by flying in and out of Dublin, and Ireland has always been high on my list to places to visit (more for the music and scenery than Dublin itself). Add to this, our daughter is going to an obstacle course event (Tough Mudder) near Dumfries Scotland two days after we arrive in Europe that we plan to attend.
Hence the trickiness. Right now I'm thinking we go from Dublin to Edinburgh on the 12th, do the castle on the morning of the 13, head down to Dumfries (at some point we will want to rent a car), we have two nights booked in the area (13, 14) now OR we could go to Glasgow and head down to Dumfries on the 12th.... For the trip as a whole, we will be going to Scotland first, then to Germany then leaving by way of Ireland. I am trying to get a handle on how much time to allocate to each part of the trip. If we split it in thirds that's 5 nights in each country, which seems a bit rushed to me. My husband I are kind of laid back and aren't going want to be on the go every minute, so while we do want to see some castles and cathedrals, etc. I think we are bigger on 'ambiance' and scenery so I am thinking of stretching out one of the Ire/Sco parts and minimizing the other, or stretching Germany (which can include Belgium and France given her location) and minimizing the other two. I know there's all kinds of options here, but if anyone has any pearls of wisdom to share I'd appreciate it. Thanks!