It really depends on how you want the
effect to
play. There are many ways to possibly accomplish something like this.
As you mentioned, the dancers could wear a rig, but that would mean that they a either wearing it for the entire piece or have to choreograph a way to get it on. This would probably provide the least
dynamic look as the doves would be mostly static around the performers. It could also be potentially limiting in how close the performers could get to eachother and what kind of moves they can make.
You could create dove puppets and have people puppet them. They could be
hand puppets or on poles. This would likely be the most
dynamic way to achieve the
effect as the puppets and performers could be choreographed in such a way as they could interact with eachother. It also would not hinder the performers.
Lastly, if you have the budget and technology, you could do projections. Design animations that
play around the performers. Obviously this would require a
projector and suitable projection surface, plus a projections designer/animator.