Loose skin can occur from rapid weight loss.
Breast size will go down with Fat Burning, as Fat is stored around the mammory area.
As for Knee Damage, poor technique on Cardio could do it, as could pounding the streets for hours a day, but if you were choosing a route that included plenty of park, grassland areas or soft sand, the impact from outdoor running should be considerably reduced; the impact of soft sand versus hard wet sand should be better.
You can get something from running Chondromalacia Patellae, A.K.A. Housemaids Knee, Secretaries Knee, Runners Knee and Patellofemoral Syndrome. It causes degredation of the Cartilage; Chondro comes from ancient greek meaning Cartilage, Malacia means softening or degredation.
You then can get sliding of the Cartilage to the lateral, (outer), side of the knee, with an accompanying kind of grating sound.
This could be reversed by strengthening exercises for the surrounding areas and reduction of the impact causing it, or cutting out the exercise that causes it for a few days.
Running shoe types should be a prime consideration depending on your action. Neutral, Pronated, (Ankle rolls inwards), or Supinated, (ankle rolls outwards), but the impact on the Knees should be slim, but something with good padding on the inside and a fairly thick sole might help; the main issues from running can include Shin splits caused by Heel striking and also Plantar Fasciitis, which is inflammation of the Plantar, the fiberous strip roughly between the Calcaneous bone in the Heel and the ball of the foot, but such things can be avoided or eased by use of orthotics.
Plantar is also caused by a tight Achillies and weight problems.
This issue should not occur with cycling hopefully, but obviously care should be taken to use a bike that provides a comfortable sit
What you're planning though should be fine
Good luck and anything else you need or anything you'd like to say to others, don't hesitate to contribute