Perhaps you are familiar with the concept of the universe being designed for life (aka the anthropic principle). But did you know that the earth's interior is also fine-tuned to facilitate life? Here is just one example, from the ScienceDaily web site:
Volcanoes Key To Earth's Oxygen Atmosphere
This article describes how geologists think that the introduction of terrestrial volcanoes was a critical factor in the production and retention of oxygen in the earth's atmosphere. From the article,
"'A switch from predominantly undersea volcanoes to a mix of undersea and terrestrial ones shifted the Earth's atmosphere from devoid of oxygen to one with free oxygen,' according to geologists. 'The rise of oxygen allowed for the evolution of complex oxygen-breathing life forms,' says Lee R. Kump, professor of geoscience, Penn State."
I would rephrase this as saying the rise of oxygen indicates the careful planning that God exercised in preparing Earth for humanity.
In developing old-earth creation focused curricula, we should be cognizant of the overwhelming evidence for the careful, fine-tuned, integrated and complex manner with which God works within His realm. Instead of questioning why God would take almost 5 billion years to get from "no Earth" to "humans", we should be marveling at how He carefully timed physical events, within the natural realm He created, to provide the just-right conditions for advanced life.
For instance, consider that the Earth's original composition would not support extended vulcanism. Consider that the moon creation event provided the Earth with the raw materials necessary for vulcanism as well as blowing off a heavy atmosphere. Consider that the increasing luminosity of the Sun has been counteracted by the combined effect of vulcanism, geologic cycle, and water cycle. Consider that the first life forms were ideally suited to provide oxygen to an oxygen-free environment. The list goes on, and on.
Some interesting reference material on this topic are:
The Creator and the Cosmos
What if the Moon Didn't Exist
Origins of Life