Again, it is a commemorative service. The re-enactors will be there to add a little color and excitement and for the general public, including children, to see soldiers dressed up in period uniforms, see some cannons, watch and hear them fire, and so on. It's planned for everyone, not just CW historians.

I believe what is causing you so much confusion is that you are trying to match a brief re-enactor skirmish that, in part, serves as entertainment for the general public, with a full scale battle planned to show details of troop positions, action, and movements for historians.

It's a commemorative and memorial service to honor the battle and those who fought in it. As an added touch, they're having some re-actors to add color for the visitors, and there's really no need to complicate it beyond that.