|From the blog, Children of Vietnam.|
As you know, as the balloon rises higher and encounters lower pressure from the atomosphere, it expands and eventually bursts. The plastic balloon falls back to the ground where it becomes a hazard to wildlife. The overuse of helium is another issue as well.
I googled alternatives to releasing balloons at funerals and discovered How to Have a Safe Balloon Release or Use a Meaningful Alternative. Check it out. To that list I would add burning incense which is part of the burial ritual of Vietnamese. (See also the blog post, Saying Goodbye.) Burning incense is also the custom in many other religions and cultures and incense is used in the burial rites of liturgical Christian churches.