August 25th, 26th, and 27th is the Hotter N Hell weekend. I am signed up for the mountain bike race (13 miles) on friday, the century ride on saturday, and the half marathon trail run on sunday?

How would you attack this? I'm waiting on my sc sensor for Trainer Road virtual power and when it gets here I'll get started on it (Base, Build, Century plan).
Was thinking about just incorporating a half marathon training plan in as well, but don't want to over do it with two separate plans.
What about a HIM plan omitting the swimming?

Should I rely on road bike fitness for the MTB portion (and just do a few mtb rides when I can)?

Thanks for any help.