There should be no problem with scaling up the ingredients (multiply each of the quantities by the number of cakes). The only time I would advise against doing that is if you are baking with yeast, but that's not likely to be the case if you are only making cakes.
Having prepared the mixture (all in one go), you need an accurate way of dividing it between the individual cakes. Probably the best way to do that would be to weigh the entire mixture (weigh the mixing bowl before you start, and subtract that from the total weight). Then divide the weight of the mixture by the number of cakes. Then add that amount of mixture to each of the cake tins.
The biggest problem will be deciding the baking time. With several tins in the oven at the same time, you need to allow more time than if you were just baking a single cake, but there's no obvious way of knowing how much extra to allow. Also, different parts of the oven will be a different temperature (unless you have a fan oven), and this adds to the complications.
What you should definitely not do is to make the mixture in bulk, then bake the cakes one at a time. You always need to get the cake into the oven as soon as possible after mixing.
Hope this helps. Let us know how you get on.
Mike