Omnhio

Thanks a lot! Here’s my approach:

Functions

if (!function_exists('groups_frontpage_widgets')):
function groups_frontpage_widgets($params) {
	$id = $params[0]['id'];
	static $counter = 0;

	if ('frontpage-widgets' !== $id) return $params;

	if ( 0 !== $counter && 0 === $counter % 3 )
        $params[0]['before_widget'] = '</div><div class="row">'. $params[0]['before_widget'];

	$counter++;

	return $params;
}
endif;

add_filter('dynamic_sidebar_params', 'groups_frontpage_widgets');

In the template

<?php // Display Frontpage Widgets
	if(is_active_sidebar('frontpage-widgets')) : ?>
		<div id="frontpage-widgets">
			<div class="row">
					<?php dynamic_sidebar('frontpage-widgets'); ?>
				</div>
		</div>
	<?php endif; ?>