Here's how to display full categories for specified category archives while having excerpts as the default. Add this code below to the functions.php file of your child theme.

full-content-categories.php

<?php
// Do not copy opening PHP tag

// Display full content only for specified categories
add_action( 'genesis_before_loop', 'wsm_full_content_category_archive' );
/*
 * Replace your-category with the slug for your category.
 * If you wish to display full post content on multiple categories then 
 * separate the slugs with commas like this:
 * 'your-category', 'your-other-category'
 *
 */
function wsm_full_content_category_archive() {
	$full_categories =  array( 'your-category' );
	if ( is_category( $full_categories ) ) {
		remove_action( 'genesis_entry_content', 'genesis_do_post_image', 8 );
		remove_action( 'genesis_entry_content', 'genesis_do_post_content' );
		add_action( 'genesis_entry_content', 'wsm_do_category_content' );
	}
}
function wsm_do_category_content() {
	the_content();
}