I wouldn't worry too much about missing a workout here and there. What, specifically, are you training for? If it were me, I'd do just the speed workout on Saturday and then double up on the endurance workouts on Sunday, but that's mostly because endurance training, in my mind, is something that lasts longer than an hour. I'm not familiar with your training plan though.
Live with intention. Walk to the edge. Listen hard. Practice wellness. Play with abandon. Laugh. Choose with no regret. Continue to learn. Appreciate your friends. Do what you love. Live as if this is all there is.
--Mary Anne Radmacher