Is it tacky to serve Hostess and Little Debbie snacks instead of a birthday cake?!

I think it's tacky if you just give it to him still wrapped. If you do that, present it in a cool way. Stack it like a wedding cake put wacky candles all over it. But I did an icecream sandwich cake a few years ago and it was effin delicious.

If you unwrapped them and piled them up on a serving plate in an artistic and intriguing fashion, it could be a cute alternative to a birthday cake. You might need some sort of icing to "glue" them together so the pile wouldn't come tumbling down.
Just putting the boxes out on a table, or putting wrapped snack cakes on a tray, would be tacky.

For our Daughter's birthday parties we served Hostess Cupcakes, at her request ,( Unwrapped and arranged on a serving tray ) It is her favorite snack and they were well received by the guests at the party. For her Sweet Sixteen, We had a cake made like a big Cup Cake .

Very much so. It may total the same as a cake so you should just go ahead and get the cake.

Yeah.