It's the work people! Mankind was created to fulfill the work of God not to copulate. It is obvious, Adam and his wife (She was named Eve AFTER she sinned) had work to complete first. (You don't party during the week if you know you have to get up in the morning. You wait to Friday night!)
Children helpers wouldn't be needed until after this initial work was completed when Adam and his wife would enjoy a period of celebration and fulfillment. Since they would have eaten from the tree of life, they would have a blessing to give their children. Now they could start a family with great enjoyment and excitement. (Remember Adam was expelled from the garden and barred from the tree of life with nothing to offer his offspring.)
After the children grew to maturity then the children would be commisioned to complete work like their parents. At the completion of their work, then they would eat also of the tree of life. This opportunity would eventually pass to all of mankind. So all of mankind would have had an opportuinty to qualify to eat of the tree of life.
Read Revelation 20:12, "...the dead were judged out of those things written in the scrolls according to their deeds." This opportunity is realized in the millenium when all of mankind is given the opportunity at LIFE!!