As a mom of twins, the ideas seem limited, but if you stop thinking "Traditional Halloween" and go with everyday pairs you'll see the possibilities are endless.
You can do cookies and milk, peanut butter and jelly or even toast and jam. All these costumes are pretty easy to create with some craft foam and some paint. PLUS you can pretty much wear them not matter what the weather. This year we are considering King Kong and the Empire State Building thanks to some shirts we bought from Klzart on Etsy.
With my twins being six, it's harder and harder to "sway" them towards what I wish they would be, but fingers crossed, they will let me have SOME say otherwise I'll end up creating another zombie and a power ranger costume, not the worst choices, but it's fun for me to get creative this time of year!