Sorry, your thread was too long for me to read all of your PPs answers @Year5For3days, but I have read all of your posts (on this thread).
I presume that most Mumsnetters, and possibly you as well OP, will think that my reply to you is "woo woo", and actually I suppose I agree with everyone who does think that. But - and this may sound like I am contradicting myself - I think that it is a legitimate woo woo fear! My thoughts are:
Many years ago, my then young child (8 y.o.) was supposed to have her tonsils out due to suffering from recurring, and horrible, symptoms of tonsillitis, we had even been given the date of the operation. But I suddenly realised that I was dreading her having the operation - and my fear for her was much more than is normal when any of one's own children are going to have an operation - my main fear was about the general anesthetic that she would have had to have had.
So I wrote to her consultant, apologising and telling him that I was cancelling her operation. Her consultant replied very quickly (I was not sure that I would even get a written response directly to me) telling me that neither he, nor any of the anaesthetists he usually used, had ever lost a patient, and he almost promised me that nothing bad would happen to her. However, my very strong feeling of foreboding did not lessen at all after reading his reply, so I did not reinstate the operation.
In some ways I wish I could tell you dramatically that something very bad did happen in that operating room, on the date my DD's operation 'should' have happened (of course in realty I would have been devastated if anything had happened to anyone else), but I am not aware of anything untoward and/or unexpected that happened anywhere on that day. My only stab at vindicating myself is that my DD - who is now middle-aged - has never had another episode of tonsillitis.
On another occassion when I was out with my DH in the evening (which was a very rare occurrence in those days), my DH was trying to find a parking space (city centre), but when I pointed one out he didn't like it as it would have been a bit of an awkward space to get into (he was a very capable driver in those days), and possibly out of as well. My DH then noticed another parking space about 100 yards further along, on the other side of the road. He went to park there, but I suddenly got a strong feeling that parking there would not be good idea. Unfortunately my DH ignored my 'feeling', and when we returned to the car about 3 hours later, the rear nearside window had been smashed and my favourite - and only - winter coat had been stolen. Luckily we had not left anything else easily removable in the car, and they didn't seem to have tried to actually steal the car.
I have had about 3 other occassions which could have been described as having "woo" connections, but which can't be proved one away or another.
Please @Year5For3days, listen to your gut on this occassion. You may never know whether your foreboding is correct or not, and you may well have a slightly dissapointed DC on your hands, along with a small lack of a particulsr experience, and an affronted DHT, but those should be about the only negatives connected with this situation.
If, however, you do change your mind OP, and despite dreading it, you do let your DD go on this trip, just imagine what your and your family's lives will be like, if the worst thing does happen and you all suffer from a tragic outcome. In my mind, and because of how strongly you feel about your DD going on this trip, please do not change your mind again -
Disappointment versus a possible tragedy, makes, imo, a very easy decision...