It's hard to imagine a geekier collection than a collection of NASA patches.
Intrinsically, all collections are educational because the GeekKid has to familiarize him or herself with the full range of information on all potential pieces for the collection. And when it comes to NASA lore, there's a lot to learn: the history of the different missions, famous astronauts, and legendary spacecraft. Can your GeekKid find the patch from the first Atlantis-Mir mission? Which patch is for the final non-Shuttle mission? Which patch has the Road Runner & Wile E. Coyote on it?
In addition to scientific stuff, you can talk about the graphic design of the patches. Have your GeekKids theorize why ITS-1's patch is simple while STS-113's is almost absurdly complex. Which patches have different flags or foreign alphabets on them and why?
Most GeekKids have a collection of some sort and this one is as good as any other, if not better - it's hard to learn anything useful with a Pepsi can collection. For parents it's great because collections usually can be set aside for a number of months or years when restless minds get distracted with other activities. Plus, contributions to the collection make great bribes to encourage good behavior.