Using 9” pans instead of 8” pans

also keep in mind the volume of the pans (6c each for 8" diameter, 8c for 9")...so if you make a cake planned for three 8" pans in two 9" pans, there will be approx 18c volume to fit into 16c pans.
Maybe scale the cake down, so it fits in the two 9" pans. Or use some muffin tins for extra batter.

you know, i think you could use two 9-inch cake pans - the layers might be a tad thicker (than three 8-inch ones) and you might have a bit of extra frosting/filling etc. (since the cake will require less due to only being two layers) but i think it will work. the two layers may bake a little longer than the 3, because they will be a tad thicker, so be sure to look out for that.