Your question is a great question, and the answer is multifactorial. First of all, are you in good health, do you smoke, do you have asthma, do you have high blood pressure and if so, is it well controlled? There are pros and cons for doing three surgeries at one setting versus breaking them up into two or three settings.
The speed of your surgeon is certainly an important component. Some surgeons are faster than others, and therefore multiple procedures can be done in a shorter period of time. You obviously need a Board Certified plastic surgeon truly experienced in the Mommy Makeover. The combination of the multiple procedures in a Mommy Makeover are definitely different than doing each surgery separately. You obviously need a Board Certified anesthesiologist and a surgeon with an experienced, dedicated team. Hospital settings where the team isn't used to the elements of a Mommy Makeover may be a very safe place to operate, but the procedures may go slower leading to the necessity of breaking up the Mommy Makeover into its component parts.
If your breast augmentation and tummy tuck are straight forward procedures (no lifts, no extended tummy tuck, etc.), and if you have sufficient fat on the back part of your body (love handles, thighs, etc.) to yield enough fat for the Brazilian butt lift, and if you have done your homework, found a great surgeon who does a lot of Mommy Makeovers, then I would say the combined surgeries may, in fact, be a very safe way to get everything done at once and skip multiple anesthesias. Post operatively, in my practice with this many procedures, I would certainly keep you overnight to add that extra layer of protection.