You could do it like this:
<a class="btn btn-primary announce" data-toggle="modal" data-id="107" >Announce</a>
Then use jQuery to bind the click and send the Announce data-id as the value in the modals #cafeId:
$(document).ready(function(){
$(".announce").click(function(){ // Click to only happen on announce links
$("#cafeId").val($(this).data('id'));
$('#createFormId').modal('show');
});
});