I dont think i can get your DS light conected to the internet because i dont have a Motorola Router. Maby if you had a DSi because thats one hundred times easier.
The fact is i dont have a Motorola router so i cant experiment with it for 3 hours till it works.
So until you get a Linksys router or a DSi I dont think I can help you.
I tried my best. After all im not a computer geek im just a guy who wanted to play pokemon with more than 1 person.
I do have an idea that might work.
You get your dad we see if he knows how to get to your Motorola Routers settings and then we go from there. I dont think he would know though. (No offence to your dad)