How can i change checkboxes from vertical align to float left?

This is my HTML code:

<label class="control-label col-md-4">Availability <span class="required">*</span></label>
<div class="field_wrapper col-md-8">
    <label class="checkbox"> 
        <input type="checkbox" name="custom[availability][]" class="reg_form_availability" value="Sunday" tabindex="14">Sunday
    </label>
    <label class="checkbox"> 
        <input type="checkbox" name="custom[availability][]" class="reg_form_availability" value="Monday" tabindex="14">Monday</label>
    <label class="checkbox"> 
        <input type="checkbox" name="custom[availability][]" class="reg_form_availability" value="Tuesday" tabindex="14">Tuesday</label>
     <label class="checkbox"> 
        <input type="checkbox" name="custom[availability][]" class="reg_form_availability" value="Wednesday" tabindex="14">Wednesday</label>
     <label class="checkbox"> 
        <input type="checkbox" name="custom[availability][]" class="reg_form_availability" value="Thursday" tabindex="14">Thursday</label>
     <label class="checkbox"> 
        <input type="checkbox" name="custom[availability][]" class="reg_form_availability" value="Friday" tabindex="14">Friday</label>
    <label class="checkbox"> 
      <input type="checkbox" name="custom[availability][]" class="reg_form_availability" value="Saturday" tabindex="14">Saturday
   </label>    
   <label class="checkbox"> 
      <input type="checkbox" name="custom[availability][]" class="reg_form_availability" value="All week long" tabindex="14">All week long</label>
    <input type="hidden" name="custom[availability][]" value="--">
    <p class="description">Please specify the week days the trip can be offered</p>
</div>

The output looks something like this, just with a checkbox on the left of every selection:

Availability * Sunday Monday Tuesday Wednesday Thursday Friday Saturday All week long Please specify the week days the trip can be offered

How can I change the selections to be on the same line floating left? Two lines is better actually (4 selections each line). If i had accesses to the HTML code I probably would have use bootstrap col-md to do so but the problem that this is a WordPress website and the HTML is not shown as it is above in the PHP files.

Thanks in advance, Yaniv