Dose that scream tacky?

NO! it's not like a birthday party or a baby shower.... you have flowers at weddings not balloons

NO screams tacky and 80's

I am going to have to say no to the balloons. You might be able to pull it off and not have a prom feel, but I would just save the money for something else.

Yeah, I like the idea or the pearl colors as well... no bright colors... period... (Ex. no red, no blue, etc.) think... gold, silver, pearl white... congrats and good luck!

I think selectively placed balloons can look beautiful. They create archways with them - in your wedding colors that would look great!
Tying them onto the back of every chair would make it too birthday-party like.

If they are metallic or pearlized. Also, stick to one or two colors.

It would not be tacky-- as look as you keep it formal.