Baking question

I am about to make my little man's birthday cake. Sorry, it is a bit of a stupid one. I have a recipe that calls for a 28 x18 tin. I have a 30 x 20 tin. Will the recipe still work if I increase the ingredients by roughly 5% (the difference between 28 and 30).  Any advice appreciated.

Almost right.  You need to work on areas rather than lengths though.  I make this 19% bigger (but I am almost asleep)

Ah, I see that now. Thank you so much PP