You are very welcome. To answer your question...Yes, certainly the deceased can receive benefit after they have departed as well as the anniversary of their death (by offering flowers etc.) to their grave site.
Buddhist's believe that the 49 days right after their death is the most important. This time-period is called the BARDO or intermediate state between one incarnation and the next.
I found a few Amitabha songs that you may like. It really doesn't matter how you chant it. What matters most is your INTENTION. The more heart-felt the feeling you put behind the words can only make it better.