Well, It's probably just your internet, and DSi/3DS's aren't really meant for that kind of thing. I found however that deleting your history makes it go a wee bit faster. But honestly, for chat you're probably going to want to stick to a laptop/PC.
The app does NOT work for the Ds/3ds Etc. You might want to bring it up to the Pokemaster to make something of the sort, though it might be complex being that all apps for the 3ds/dsi work through the E-shop, and he'd have to work that out through nintendo.