My 10-year-old son is studying the great continental divide in school--how does that relate to creationism? His teacher said it doesn't affect your view of creation, even though she is claiming it happened millions of years ago.
The fact that the great continental divide exists and how it got there are two very different issues. Honestly, for a 10-year old, he can probably learn all he needs to know about the divide without needing to debate how or when it arose. If the geological development is part of the lesson, your son can always regard the timeframe a separate issue, or simply resolve to understand how most geologists explain it without committing himself to accepting their entire explanation. I would recommend he learn what is required of him and simply resolve to keep his mind open to the timeframe issue. Creationist flood-model geologists would explain the rising of the Rockies (hence the continental divide) by the same mechanisms as evolutionary geologists, just over a much shorter time frame.
Hope this helps.