A birthday cake recipe for 30

Hi there, I posted a couple of months ago about hosting a surprise buffet lunch for my mum's birthday, and it really helped me figure out what to serve - however I have the problem of the birthday cake.

I do have cake recipes, but they generally serve around 8-10 people so I don't want to have to make 6 8in cakes. I am also not sure about doubling or tripling recipes in one go ...

Do you think that if I made 2 13 x 9 x 2 cakes and stacked them, that would work out ok? If so, does anyone have a good recipe - from scratch not boxed - for this quantity.

If this is not a good suggestion, does anyone have any other ideas?

I want a relatively plain sponge cake, not chocolate - not one that requires a really creamy filing (was going to just fill with either lemon curd or jam).

I should also say that I don't have a stand mixer - if that makes a difference to any suggestions, and also that I am in Scotland and the cake will be being made in the middle of May (in case of seasonal suggestions)

Thanks once again for your help Chowhounders!!