I think it is def doable. If that is how much you want to spend stick to it. I would reduce the alcohol a little bit. For example, do you need to drink every day? If you only drink every other day that will save you $100 right there. I think that tips will probably run closer to $150 rather than $100. If your dds have birthdays/other holidays coming up ask for Disney Dollars from your family/birthday guests. If you have a Disney credit card, you can earn Disney dollars on it for every dollar that you spend.
I don't plan on spending more than a couple of hundred outside of food but we are not big souvenir people so I am saying yes, stick to your budget-everything else is paid for so you should have a great time even sticking to a budget.