Get the value from the XML SQL Select Statement

I am being trying to understand and learn how to take value from XML. I have taken a reference of an XML document from the link below.

Link

In order to get clarification I have removed some of the unwanted xml parts.

Example

 <?Label VCAT|RESERVATION|21405|SUCCESS?> 
<Reservation xmlns="reservation.fidelio.4.0" mfShareAction="NA" mfReservationAction="EDIT">
    <reservationID>11650</reservationID>
        <GuestCounts>
            <GuestCount>
                <ageQualifyingCode>ADULT</ageQualifyingCode> 
                <mfCount>1</mfCount> 
            </GuestCount>
            <GuestCount>
                <ageQualifyingCode>CHILD</ageQualifyingCode> 
                <mfCount>0</mfCount> 
            </GuestCount>
        </GuestCounts>
</Reservation>

In HTML, For Example google.com - To target input for that Page we use XPath as //input[@name='q']. Similarly inorder to target a node we can specify //ageQualifyingCode to get value within that node. So based on that I have created a query specified below. Can anyone tell me what's wrong with this query as I am getting output as NULL.

   DECLARE @XmlDocumentHandle int 
DECLARE @XMLData XML
SET @XMLData ='<?Label VCAT|RESERVATION|21405|SUCCESS?> 
<Reservation xmlns="reservation.fidelio.4.0" mfShareAction="NA" mfReservationAction="EDIT">
    <reservationID>11650</reservationID>
        <GuestCounts>
            <GuestCount>
                <ageQualifyingCode>ADULT</ageQualifyingCode> 
                <mfCount>1</mfCount> 
            </GuestCount>
            <GuestCount>
                <ageQualifyingCode>CHILD</ageQualifyingCode> 
                <mfCount>0</mfCount> 
            </GuestCount>
        </GuestCounts>
</Reservation>'
EXEC sp_xml_preparedocument @XmlDocumentHandle OUTPUT, @XMLData  

SELECT *  
FROM OPENXML (@XmlDocumentHandle, '/Reservation/GuestCounts/GuestCount/',2)  
WITH (ageQualifyingCode     varchar(10)   '//ageQualifyingCode',  
      mfCount  int '//mfCount')  
EXEC sp_xml_removedocument @XmlDocumentHandle  

I have also tried using XQuery mentioned below but no result

SELECT * FROM (
SELECT TOP 1  
X.Y.value('(ageQualifyingCode)[1]', 'nvarchar(50)') AS ageQualifyingCode, X.Y.value('(mfCount)[1]', 'int') AS mfCount
FROM #temp1 t
CROSS APPLY t.xmlBody.nodes('Reservation/GuestCounts/GuestCount') AS X(Y)
) T

Also, how will I be able to target reservationID in same cross apply?

Output

+---------------+-------------------+---------+
| reservationID | ageQualifyingCode | mfCount |
+---------------+-------------------+---------+
| 11650         | ADULT             | 1       |
+---------------+-------------------+---------+
| 11650         | CHILD             | 0       |
+---------------+-------------------+---------+