I knew I'd get some good advice here. Thanks.
My first decision is to not push anything on the bike or run past 'always enjoyable' until I have a few months of training in the book.
I also think I'm quite good at listening to my body. I cancelled yesterday's evening run as I felt the morning's cycle had been enough for my legs and I am also willing to walk if my legs are asking even if my breath and heart feel calm.
A major concern was to not imprint bad habits, especially where stride length was concerned but that doesn't seem to be something I need to be over concerned about.