D. H.,
In idea, for your "play-time," maybe 2-3 times per week, put your son in a stroller and you and him go outside for a walk. Maybe just a block or two to get started. In addition the cardio workout you'll get the outdoors will be great mentally for both of you. You may also find out other moms are doing it already or may be interested in walking also.
Another idea, get a pilates VHS tape or DVD and play it in your living room for 15-20 minutes the other 3 days in your week. Alternating your walk-days with pilates days.
Eat smart and drink plenty of water.
Be sure to let your OB & Health Care Provider know of your exercise plans/goals.
Feel free to e-mail me if you have questions at ____@____.com luck D..
D. P., LMT, CPT
Massage Therapist
Personal Trainer
Fitness Instructor
Birth Doula