http://www.jonathanmaim.com/2008/03/setting-up-dns-of-your-google-apps.htmlResumindo :
* A Records
@ A 72.14.207.121
@ A 64.233.179.121
@ A 66.249.81.121
* CNAME records (don't forget the trailing dot at the end)
www CNAME ghs.google.com.
calendar CNAME ghs.google.com.
start CNAME ghs.google.com.
mail CNAME ghs.google.com.
docs CNAME ghs.google.com.
sites CNAME ghs.google.com.
* MX records (don't forget the trailing dot at the end)
MX 10 aspmx.l.google.com.
MX 20 alt1.aspmx.l.google.com.
MX 30 alt2.aspmx.l.google.com.
MX 40 aspmx2.googlemail.com.
MX 40 aspmx3.googlemail.com.
MX 40 aspmx4.googlemail.com.
MX 40 aspmx5.googlemail.com.
No teu caso só precisas de apontar o address record e o cname www.