It really depends on a few factors. Adequate pain control is likely the most important. Individual pain tolerance differs greatly. I find that women who have had children generally have less post-op pain, as they have a much higher pain tolerance. From a surgical point of view, there are several things the surgeon/anaesthesiologist can do to decrease your post-op pain.
I generally perform breast blocks prior to making any incisions with a mix of short- and long-acting local anaesthetics. I have found this greatly reduces post-op pain. I also encourage patients to take the prescribed pain killers regularly every 4 hours especially for the first 24-48 hours. If you don't stay on top of the pain in the immediate post-operative period, it is extremely difficult to "catch-up". Most of my patients experience very little post-op pain after breast augmentation.
Of course, the type of augmentation you have will also determine your post-operative discomfort. Larger implants, and subpectoral implant placement will also increase post-op discomfort. This doesn't mean you shouldn't get large implants, or place them under the muscle - you simply need to know what to expect. Many women also experience difficulty with sleeping in the first few weeks after augmentation due to the weight of the implants on their chest. This is more significant in back-sleepers.
To answer your question about time off work, my experience has been that there is a huge range. I have patients that go back to work the next day (against my advice), and I have had patients take as much as 2 weeks off of work. It really depends on what you do for work, and how you feel. As for taking care of your kids, if your implant is placed under the muscle, it will be a few weeks before you feel comfortable enough to pick them up.
As for scars, I tell patients it will take a year to see the absolute final result. Practically, however, by 3-6 months the scar will be very close to the final result. I suggest 3M paper taping, and have a specific scar massage protocol I use to help speed scar resolution.
I hope this helps. Good luck!