I am a little late with this, but Red Hat has an online tool (I've seen a couple other downloadable ones) to check for the presence of this vulnerability on the server side (the vulnerability needs to exist on client and server for a successful exploit) located here. Interestingly, all the Nintendo domains not hosted on Amazon EC2 (there are a few, mostly for 2nd/3rd party stuff like Pokemon) are affected. This also confirms that Nintendo is using OpenSSL on their servers. Still no confirmation of OpenSSL on the client side, but it could be useful to know for sure that their servers are running OpenSSL in case of future exploits.
I will stay on the lookout for a way to test for this vulnerability on the client aka (3)DS side. The information is out there for people a little more inclined than I am, so I expect one will pop up soon.