Trying to organise a once in a lifetime trip to Colombia for next Christmas with my family of young adults. We have worked out that it would be cheapest to fly out on Fri 11th Dec so that they all only have to take 2 weeks annual leave but have 3 weeks away due to Christmas close down. The outlier is my youngest who is at university and won’t know exam dates until a month before in mid November. So 11th might be OK for them - or they may have to fly out and join us a couple of days later. We are paying for all of the flights (8 in total) so need to keep costs down. Does anyone have any experience of an airline that will allow to change a flight a month before at a reasonable cost?