My kids (turning 5 on our trip and turning 9 on our trip...2 May babies!) have also been saving their money for months. They each have $25 in Disney Dollars, and my 9 y/o has about $30 in cash. My 5 y/o has NO cash, so we'll be making up the difference for him. I expect with Easter coming, plus their birthdays, they'll each get a few more Disney Dollars. With that said, they will both be going to Disney with $80 ($10 a day) and that's it. We've already told them that we'll buy them each one gift while we are there since they are each having a birthday during our trip, but that is it. The rest of the souveniers they want will come from their own money. When it's gone, it's gone. We've been talking alot about making good financial choices...thinking about what you buy first, whether or not you will play with it, use it,etc. My 9 y/o has been very receptive to this. My 5 y/o doesn't "get it" and will probably need a lot more help and prompting to make the right choice. Even though it's their own money, I don't want to see them buy things that are going to end up broken and on the bottom of the toy bin when we get home. We'll see how it goes.
I have no problem getting my two into gift shops. If they know there is something in it for them, they are right in there. They LOVE to shop and I actually wish I could keep them OUT of the gift shops! It would make my life a lot easier!
As for my dh and I, we don't buy any souveniers so I don't even budget that. We both have t-shirts from previous trips that we still wear, so no need for more!