In this video guide I will show you how to hit two opponents with a single bowling bomb. This can be done on any map during adventure mode, or arcade style. Now to make this easier your going to want to get all 10 wampa fruit. It might be easier to just find a crate that gives them to you and wait for the the AI to leave. Gather your 10 from the same crate since they spawn back pretty fast. Then move on to a weapon crate and keep on wasting the weapons until you get the single bowling bomb. Not the one that gives you three, but one. Once you have that and the wampa fruit wait for the AI racers to go by. Try to aim for a group and you should get multiple since its powered up and has a better area of effect.
Now if you are having problems on some maps try Coco Park since the ares is pretty open and the AI racers tend to be in some small groups. Once you see two racers rolling from being stunned by the bowling bomb the achievement will pop.