I have a lovely, but reactive dog. He isn't aggressive, just very shouty when he feels excited / nervous on lead when he sees other dogs. Off lead he is fine. He isn't big, around 11kg.
Although he hadn't shown any aggression at all to anyone, or anything, I was very anxious. I introduced baby gates early, got him used to the baby equipment, and agreed with partner that we were going to be super hot on their interactions.
When I brought my son home the dog was an absolute nightmare. Barked constantly, kept trying to lick the baby, was really unsure of his new situation. We used lots of treats, gave dog his own space to retreat to, kept them separate at times and together when both of us could supervise. It was impossibly hard training a nervy dog whilst recovering from the birth, but after a few weeks the dog got used to the idea and he stopped trying to constantly lick him. I never really let dog and baby be on the floor in the house together, mainly because it sent the dog into lick mode.
We still separate them, mostly because my son is a very quick toddler who charges towards the dogs yelling his name, but they go on walks together, have garden time together and have supervised (for the dogs sake!!) time together. Dog is besotted, so is my son, and now toddler can throw balls he has figured out a way to interact, which is all he wanted to do. When dog now tries to lick, the toddler just pushes him away so he is respecting that as he does adults now.
I think in your situation with the huge size of your dog I would be even more careful, get a professional in early in keep an eye on the dogs body language. Don't worry about separating them, dogs get used to it as long as they get walks and attention. It's time for them to safely snooze. :)
One side note though - I can never let my dog off lead around toddlers anymore because he thinks they are the best thing since sliced bread. He used to ignore them.