There's countries with 3 athletes and have 10 people march in.
Considering the very hard work of these coaches who work so close with these young people and give of their hearts through great skill and professionalism and care, I don’t see why NOT they should not march. They are part of the team officially. So put it to a vote to the atheletes themselves, and only themselves, whether they want Coach along with them in all that glory they have jointly worked for, for nearly four tough years.