With the cake there are 3 options really - 1. make it all from scratch 2.make a packet cake or 3 buy a sponge and decorate it.
You can get some tins that are already dora and you just try and copy them but i find out here you cant hire any and they are expensive to purchase and only use once. So i would make a large square one (or buy one depending on what you want to do) get a piece of paper and cut out the shape of dora's head and use that as a guide to cut out your cake. Then you can ice it with normal butter icing (mixed in different colours and piped on so you get it in the right spots) or you can use different coloured fonants. Then you just use lollies/licorice/chocolate to decorate.
It doesnt really matter what it looks like at the end of the day...the kids will love it either way!!
As for recipes, what type of cake do you want to make? Sponge/chocolate/mud/marble?? Than i might be able to help you with recipes.