Is it possible for someone with edwards syndrome (trisomy 18) have children in the future if they live long enough?

Maybe. This is complicated. First, in most cases, there is an extra chromosome in all cells so the sperm and eggs will be genetically defective anyways & so can't create an embryo. Rarely, one can have mosaicism in which some cells have trisomy 18 - theoretically, the sex cells could have the normal 23 pairs. However, there's also anatomic problems like undescended testes in males. So the odds are low.
Wouldn't think so. Since one has never made it to puberty I think the answer is obvious. .
Genetics consult. Ask your question the office of rear disease research here: http://rarediseases.Info.Nih.Gov/gard/ or genetic consult.