I agree with Subedei. I always take about that amount and come back with loads but I haven't got someone with me who is continuously asking (can I has this, can I have that, I must have) or have I ? . The answer would be no anyway
Food and drink are really cheap out there. As for souvenirs, not really much for kids until you are getting speedway related items.
Watch out for people trying to exhange money on the streets. Better to go to a bank if you need more Crazysue. Hope to see you both there.