What's a good post pardum workout routine?

First of all, congratulations. Based by your writing you are very happy. As to your question the issue is one of clarification. Exercise is to fitness as diet is to weight control. Far too many people confuse the issue. In your case, your physical limitations with the knees are an issue that is best addressed by professionals. The first one is your doctor who knows and has x-rays and MRI test results as to the actual condition of the knees and as to what specific motions are to be totally avoided. For example, riding a bicycle is easy on knees compared to even walking. But that may not be advisable. Swimming is known to be an excellent total workout but I do not know if you can swim or if you have a decent size pool available year round for swimming or even water aerobics. Dancing to the various routines like Zumba is possible if your knees can sustain dancing. Finally, since upper body strength routines do not use the knees, there could be a serious of exercises for wheel chair bound people that can be directed to your use. Again, it is best to have a medical certification as to what you can do and then you can select what is appropriate, convenient and manageable for your situation. One last thing, with a child to take care of, will your knees be up for the job? Best wishes.