If you want to do more, you could change the Monday routine and run instead. But do not run more than 4 days/week! It will only lead you to easily get injured.
On the other side, if you feel your body is rusty, the routine is too hard for you and you need some previous sessions, these walking routine might suit you better to get your muscles started. The good thing is that it is possible that you can do the 5K as well since there is normally a category for walkers:
GET EQUIPPED! Right now you are at the very beginning, about to enter the runner’s world. Buying a few clothes will keep all the excitement high about this new sport. But for now, we will recommend you to keep it simple: get some good socks, a watch, comfortable clothes and a nice pair of running shoes. (be ready to answer the question: are you pronator, supinator, neutral?) In the future, you will have plenty of time to buy more stuff!
Another important point to take into consideration is to TAKE IT EASY. Do not over train (it will only lead you to fatigue, pain and injuries), and start from the very beginning. What I mean is that you have to train from where you are right now, not from where you would like to be. Otherwise, you will feel overwhelmed too easily and you will end up quitting.