I would leave the 6 month old at home too. Far far too young to bring.
Hotels at Disney Paris include breakfast, so what most people do is make up rolls with ham and cheese for lunch. Everyone does it. There is a Centra type store just outside the entrance (beside the train station) which does good reasonably priced food, crisps, bottled water etc. There are also water fountains around the park so you can fill up water bottles, although don't rely on them as they don't always work.
You can buy meal deals at the hotels - where you buy meal vouchers for one or 2 meals per day of your stay - you can either use them at the hotel, or in any of the restaurants at the park (I would recommend eating at the park, then bringing DC back and putting straight to bed).
You can also hire prams for use in the park - I think for €5 a day, but the one thing I would recommend is bringing a bicycle chain for the pram, as people pinch them.
When our DC were that age, we would generally have just stayed in the room once they had got to sleep, reading. In small hotels we would have gone downstairs and left the baby monitor, and checked every 30 minutes or so, but these Disney hotels are massive.
IIRC if you want to use the fridge for milk etc, you need to ask the hotel to unlock the mini bar.
Finally, if you are staying at the hotel, you get entrance to the park at 8.30 (although only some rides are open). Make the most of this, and be at the gate for 8.30. We went on the Peter Pan ride loads, with no queue at all, yet once the park opened at 10.00, the queues were enormous. Similarly, make the most of the fast pass machines - get your passes and come back 2 hours later.
I'm sure I will remember loads more tips, but enjoy!