Setting up something on SRC is pretty last minute so I probably won't be able to put a ton of effort into it as I'd like.
This is the CastleMania website: https://castlemania.run/
You can view whatever on there. Feel free to offer advice for its appearance or if you find any spelling errors or bugs feel free to let me know.
For actually registration the link would be: https://castlemania.run/register/
I'll try to include as much as I can here, when I can, but I'll probably be busy right up until the actual marathon.