Just remember one thing -- do Not wear your money belt or neck wallet on your person through security. It will trigger a body search and luggage and backpack search for sure. You can load your money belt any way you want, but before you reach security, you will have to find a place to put it.
I put mine in my carryon luggage, in the main section not in the outside pockets. I also carry a RS Euro flight bag and have zipped it up in there. Put it in a bag going into the cabin with you. Any luggage or bag going in the cabin first goes on the conveyor belt through X-ray. You could put your money belt in your backpack (if that's the only bag going into the cabin with you) right before you place it on the conveyor belt. So your money belt will be inside the carryon or backpack as it travels on the conveyor belt to X-ray. Just do Not wear your money belt on your person through the human scanner cause you will get flagged.
Is this a carryon luggage? You can lock it using that special TSA lock. Security has to be able to unlock it if they wish to search it. You can also use the TSA lock for your backpack. I have used them through security with no problems.
Now after security you'll want to remove your money belt from your bag and place it back on your person. This is where people differ. Some recommend going to the washroom for privacy. I did that until I accidentally dropped everything in the toilet trying to fit in a tiny stall with my flight bag and carryon. I can't imagine fitting into a tiny stall with a baby. So don't go in the stall. Stay out in the sink area or little lounge area or the baby change area and put your money belt on right there where you'll have space.
The other alternative is to do what I do; although you may get a lot of flak from the readers, it works for me. Right after security I just remove my neck wallet from the bag and put it on my person right there. After security there are usually benches where people can sit. You can sit down and place your money belt on your person. That way you don't have to walk anywhere. And it'll look like you're adjusting the baby carrier or something. Can you make your money belt lighter and more flexible? Can you put your phone in your backpack or carryon bag?
And take seriously the recommendations here for a private driver from the airport to your hotel. With a baby, backpack, and luggage, you do Not want to navigate the Leonardo Express. And I think you will be a target for the hack "taxi" drivers (they are Not official taxis) who will escort you to their "cabs" (they are Not cabs) and charge you an arm and a leg. Now is Not the time to prove you can do it. Get a recommended private driver to get you, baby, backpack and luggage safely and quickly home to your lodging.