Forbidden Snowflake
take it out on me
I believe the 3DS supports WPA, not just WEP. 5th gen games were able to take WPA (unlike 4th gen - only the DS around then so it only worked with WEP), so X&Y should too. If the connection works on your 3DS, it should be fine for the games too.
If you still can't get a connection to work with your 3ds then try looking at Connectify Hotspot (google), it's something you can download for free and will basically rehost your wifi in a different form. That might be able to help you out.
Now for exmaple, I've been testing my local hotspot. It does support my 3DS, but not my SS itself. How can I not know that it wouldn't happen the same with X&Y?