On top of Auto Text, if you would like button selection, you can create a few sets of macros and place them on the Ribbon. A macro example for this would be:
Sub oTrusts()
'
Dim oDoc as ActiveDocument
'
Select Case Control.ID
'Inserts selection of trust type 1 or trust type 2 after the mouse cursor.
'
Case Btn1
oDoc.BuildingBlockTypes(wdTypeAutoText).Categories("Legal").BuildingBlocks("Trust1").Insert Selection.Range
'
Case Btn2
oDoc.BuildingBlockTypes(wdTypeAutoText).Categories("Legal").BuildingBlocks("Trust2").Insert Selection.Range
'
Case Else
'Do nothing
End Sub
Now, the trick is to add the drop-down using Custom UI Editor. With some simple XML, you can create a new tab on the ribbon that can contain several groups and buttons/dropdown menus.
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<customUI xmlns="http://schemas.microsoft.com/office/2009/07/customui" onLoad="RibbonControl.Onload">
<ribbon>
<tabs>
<tab id="CustomTab1" label="LEGAL AID">
<group id="CustGrp1" label="GROUP 1" >
<gallery id="Gallery1" size="large" imagemso="">
<button id="Btn1" label="Trust Wife" size="large" image="LegalStyle1" onAction="RibbonControl.MyBtnMacro" />
<button id="Btn1" label="Trust No One" size="large" image="LegalStyle2" onAction="RibbonControl.MyBtnMacro" />
</group>
</tab>
</tabs>
</ribbon>
You can import images for the buttons using the Custom UI Editor. With a bit of research you should have it down in no time. Feel free to ask more questions here if you have any.
Edit: Also, there is code to add a quick part to a specific gallery and category. 
Sub CreateLegalQuickPart()Dim oRng As Word.Range
Dim oTmp As Template
Dim oQP as String
'Prompts for a name for the Quick Part
Set oQP = InputBox("Name of Quick Part:", "Prompt!")
'Place the name of your template within the quotes
sPath = Options.DefaultFilePath(wdUserTemplatesPath) & "LegalTemplate.dotm"
Set oTmp = Templates(sPath)
oTmp.BuildingBlockEntries.Add _
Name:=oQP, Type:=wdTypeQuickParts, Category:="Legal", _
Range:=oRng, InsertOptions:=wdInsertContent
lbl_Exit:
Exit Sub
End Sub