Congrats again! You are doing fabulous. Beyond fabulous actually.
Start small with the walks and work your way up. Like go for 1 trip around the block the first few days, then add another block for a week, etc. Maybe only bring 1 dog at a time at first until you feel more balanced. Any chance of an appointment with a physical therapist/athletic trainer/personal trainer to give you some ideas on exercise to build muscle and balance?