You don't even have to do the Ebay thing, if you go to many supermarkets they have smaller booklets you can buy based on various themes (e.g. the kids one has waterpark vouchers, family restaurants etc). There is also an alternative brand come out but their name escapes me at the moment. The smaller booklets are found normally at the checkout.

In terms of eating, having been in the States in the summer I was surprised how expensive it was there these days, especially as you are expected to add 15%-20% in tip. You'll pay top dollar at the big hotels in Dubai, but elsewhere it's actually pretty reasonable - along Beach Road there are loads of little cafes and restaurants, as above Satwa and Deira have some good Asian food and even in more expensive areas like Dubai Marina you can still get a decent family meal on JBR Walk or Marina Walk.