I have taken my 4/4 from the UK to Greece, with stops in Germany, Austria, Italy etc. This was done over a three week period. There were days where I drove. 8-10 hrs with others being only 3.
During the time I lived in Germany I would take whatever company car I had at the time on a road trip to Greece and loved it! Since getting the Morgan and moving to the UK, I wanted to do it again with the 4/4 and had it on my bucket list.
Am I happy I did it? Absolutely. Would I do it again, never, at least not that far.
The biggest draw back is that a classic Morgan, for me at least, is not a grand tourer. It is comfortable for shorter trips but covering the ground I did during a hot summer made it a bit of a pain after a while. The only saving grace was I had decent stops planned along the way. On smooth motorways it was pleasant and I did come away being pleasantly surprised that it felt more composed than I imagined.
The other negative was the worry of my luggage being stolen even though I had security wire mesh like bags etc locked to the chassis. As you are going with a group, hopefully someone has room for your bags so at least you do not have that to worry about that when stoping for a bio break, rest etc.
One thing I will say, the further into the EU I got the more astounded people were that this little car from the UK was there and were very complimentary of the Morgan.