When I went to Auschwitz in 1993 one of the most upsetting things was the attitude of the visiting groups of Polish teenagers - laughing, playing around, in one case they were posing in front of the wall where prisoners had been executed, and staging mock executions. Massively bad taste, and I assume it was because they hadn't chosen to go on these trips but had to go as part of a compulsory curriculum.
I'm not suggesting your daughter's group would do anything like that, but it does indicate to me that when groups go to concentration camps they need to be a bit older, 16 or 17, and it should be entirely voluntary with no pressure to take part.
My kids are growing up in Germany - there is a concentration camp (Sachsenhausen) about 30 miles away which I went to many years ago. I don't think DD1 at 12 would be ready for it yet, and Auschwitz, as a location for industrialised mass-murder, is much more traumatic than that one. I don't know at which age they 'cover' Nazism and the Holocaust in school, but it certainly hasn't been mentioned yet.
I also think it's a shame that they would be going only to Auschwitz without seeing the other side of Jewish culture in Germany and Eastern Europe - it's much more instructive and worthwhile to combine it with a visit to the Jewish Museum in Berlin, for instance, which emphasises Jewish life and religion over hundreds of years in Europe; that for me somehow makes the devastating loss all the more real and tragic, but it's also important that the Jewish people in Germany are not solely seen as 'victims'.