Split 2 checkboxes per row in GWT Panel

Question

I am using DisclosurePanel in my GWT widget along with UIBinder.

In that Panel i am adding 3-4 checkboxes as shown below.

Test.ui.xml

<g:DisclosurePanel headerText="header" open="true" animationEnabled="true">             
<g:FlowPanel>
    <w1:Field name="uiAlert1"  fieldHelpText="HelpText">
        <g:CheckBox ui:field="Alert1" />
    </w1:Field>
    <w1:Field name="uiAlert2"  fieldHelpText="HelpText">
        <g:CheckBox ui:field="Alert2" />
    </w1:Field>
    <w1:Field name="uiAlert3"  fieldHelpText="HelpText">
        <g:CheckBox ui:field="Alert3" />
    </w1:Field>
</g:FlowPanel>              
</g:DisclosurePanel>

I want to split all the checkboxes in 2 checkbox per row.

How can i achieve this? What element of GWT i should use inside my DisclosurePanel?

I have seen HorizontalPanel and few others as well. But i am not sure what could be the best way to achieve this.

Thanks!