Cross training is always excellent. It keeps you fresh and your enthusiasm up. It can't
(ultimately
) be a substitute for the distance and endurance training you need in your specific legs--but it has always improved my overall fitness and aerobic level and enjoyment--so keep it up.
It is absolutely not a problem to do two trainings on the same day. On some other post that asked how many workouts are you doing a week, some folks do 17+
You just need to know how to pace yourself, how to break up your workouts. I usually do two a day. But I don't often combine biking and running on the same day, so I can get a little leg rest. Unless I'm doing a brick or have a long weekend workout planned.
Typical week is like this.
Monday: run in am, bike in pm
Tuesday: long run, weights
Wednesday: swim, pilates
Thursday: short run in am, swim right after work, long bike train in pm
Friday: rest, or short bike train in pm
Saturday: long workouts, bricks, hikes, etc.
Sunday: long run, weights
Go with what is comfortable, and be careful to listen to your body!! Be sure to have fun!!
Dana