I just booked a scan for xmas eve. I really want to do an 8 week scan because I've had a mmc before and there is no worse feeling than knowing you've been carrying around a baby that died and all the while were happy and oblivious. It's very hard to think of anything else... It was much easier with my first pregnancy. I chose xmas eve because I will be 8 weeks exactly and I want to know before xmas in case I crack and tell someone. If the baby doesn't survive I will have three days surrounded by family for support (hopefully: they may not be keen on this baby but love me anyways) As for bad memories... I had waited 8 weeks to tell my family about my second pregnancy because it was fathers day and I thought it would be a fun surprise... I found out fathers day morning that the baby had died ( I went to emergency the night before due to bleeding). Im glad that I will always remember when it happened because ultimately it was still my child if not physically at least mentally.
So besides all that, if it is a necessary dating scan earlier is better in case they need to book a second for comparison.