Food and souvenir costs in london and paris?

My husband and I are going to London and Paris next year (July) coming from California. I just need to know how much money to bring for food and souvenirs, we are going for a week, we are both easy going, like easy cheap food, maybe a nice dinner or lunch, but mostly very budgeted, we are more interested in the scenery. I want to get a nice snowglobe from London and Paris, and maybe some other cool small things. I was thinking of bringing $350 for Souvenirs and $320 for food, EACH. is that enough?