Waiting till day 6 for egg transfer

Hi all I hope everyone is well. I'm currently going through ivf and always thought that egg transfer would be on either day 3 or 5. We made it to day 3 with 2 top quality embryos 1 average quality embryo and a slower grower so the clinic booked us in for a day 5 transfer. When we arrived at the clinic day 5 we were told we have two embryos left, but they were unable to grade at that time. Our options were transfer both and see what happens with a likelyhood of 30%-40% twins or wait one more day which is day 6 so that they can grade them and put the best back and freeze one if possible . We have picked option two because I would preper them to be checked and graded rather then have the 2ww. Has anyone else had to wait or been recommended to wait for a 6 day transfer because they haven't been able to grade on day 5? Any feedback is much appreciated xxx