SLameN,
<!DOCTYPE HTML>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<script>
function showSpoiler(obj)
{
var inner = obj.nextElementSibling;
inner.style.display = inner.style.display == "none" ? "" : "none";
var input = inner.querySelector('input');
input.checked = inner.style.display != "none"
}
</script>
</head>
<body>
<div class='spoiler'>
<input onClick='showSpoiler(this);' value='показать' type='button' />
<div style='display: none;'>
здесь скрыто
<input type='checkbox' name=name_2[]' />
</div>
</div>
<div class='spoiler'>
<input onClick='showSpoiler(this);' value='показать' type='button' />
<div style='display: none;'>
здесь скрыто
<input type='checkbox' name='name_1[]' />
</div>
</div>
</body>
</html>