two possibilities. I am not sure, but I would go for executants.

An executor is the person who complies with legal formalities.

You may be appointed executor of a deed or document at one time, fail to take advantage of the opportunity, and pass on the task to another (or to a court by default) who settles it against your interests (in wills, for example, this happens.) Then you lodge an appeal, or sue as a plaintiff for tort in arbitration. (Actually, it's your own fault, but you may have your reasons).

"Ejecutantes": according to that article they can decide how much they can ask for. "Ejecutan", "deciden" what can be charged.
It's badly used in this context because, as the English word, it means "artist", normally referred to music.
I would use the word "performer", nevertheless, because "perform" means

"vb.
1. to carry out or do (an action).
2. (tr.) to fulfil or comply with: to perform someone's request", so I a "performer" is in this context just somebody who does something.

"Actor" is a common way of calling the plaintiff.

In my reference:

"...al actor cuantificar su pretensión, cuando no exista norma imperativa que lo impida o que señale la forma de concretar el valor de la demanda, conforme a reglas predeterminadas, cual ocurre con las del art. 489 de la LEC., es visto que por propia voluntad del ACTOR, aceptada por la parte contraria y por el órgano jurisdiccional de primera instancia, viene vedado el acceso del litigio al recurso extraordinario de casación, por no exceder la cuantía del litigio de los tres millones que fija al efecto el art. 1687-1.º de la Ley de Enjuiciamiento Civil"

Hope it helps, the text is horribly written in Spanish.