Fit in the workouts as you can during the week.
Make sure you have sufficient rest included and eat well and drink lots of water.
The one thing to make sure you get right is to have 3 hours plus between your Interval Training and your Crossfit WOD.
You can do your WOD and Strength Training in the same session.
Links to the Crossfit Endurance Website
http://www.crossfitendurance.com/faq
http://www.crossfitendurance.com/legend