Pretty sure they'd want people in the prime of their life, not people with grown children.
All depends on the cost-benefit evaluation at the margin. To fill the resource, the prime candidates may be too few to recruit, and the people with grown children still relatively young and healthy available to make the trip and contribute sufficiently.
Recall the older generation that cleaned up at Fukushima.[0] These are folks that knew their activities would be uncomfortable, may cause their death, but ultimately was absolutely vital to the benefit of all mankind.
This view on life is not constrained to a single culture or background. Self-sacrifice in such a way is often considered the highest pinnacle of morality -- even under the auspices of selfish genes since the act does not directly benefit descendants. Planting trees in your later years that the fruit may be enjoyed generations after.
You may ask if I have any special skills. I do, but suppose I don't. In such a place you will need grunts. And I'd be happy to join in to build humanity's insurance policy to be a bit broader.
[0] http://www.cnn.com/2011/WORLD/asiapcf/05/31/japan.nuclear.su...