I think $1000 per month per child is reasonable, with a majority of that going to childcare, healthcare and food / diapers. When we were doing our taxes last year, we went back ten years and totaled the costs of childcare since we had our now ten year old and it was just under $160,000, but that has been for our 10, 8 and 3 year olds combined. At one point we were paying $485 per week for the three of them, and in our area (FL) we can expect to pay $150 - $200 per week for a new born.
I have excellent health insurance with my employer and pay $120 biweekly for our family of five. Our plan costs the same if we have one child or three, and if it was just my wife and I it would be a quarter of that. You will definitely save money on food, diapers and other things related to your new baby by buying in bulk, buying off brands (we saved a ton of money by using Target brand diapers vs Huggies) and linking up with others with children, accepting hand me downs and shopping for deals as children's items are always available on sale.
Also be aware children will constantly be at the doctors office for the first few years (ear aches, colds, tummy aches) so be prepared to take them in for treatment at least a few times a year. With a good healthcare plan though, usually you will only be responsible for a co-pay and some prescriptions (and your time off of work).
So the monthly totals would be something like:
childcare: $600 - $800
healthcare: $90
food / diapers: $100 - $150
misc expenses: $50 - $100
totals: $840 - $1140
Also, keep in mind these numbers are for a healthy child. If a special needs child were to be put into the equation, these figures could double, triple .... Don't mean to throw that into the conversation but it's always something to have to plan for if it were to happen.
These figures are also for a young child so don't forget the additional expenses as they grow older (bikes, sports leagues, vehicles, insurance, college, weddings, vacations). Those expenses will make your $1000 per month toddler budget seem like a deal, but in true MMM fashion there are ways to cut those expenses too.
Hope that helps!