I have had both the regular flu vaccine and the H1N1 vaccine. The only difference I noticed was that my arm was sorer after the H1N1 but that was probably because they used a larger and longer needle.
At the moment my 6 1/2 year old grandson has the H1N1 virus. He had the regular flu vaccine and needed to wait 21 days before getting the H1N1 but unfortunately he got it before he could get the vaccine and it could work. He had a 105.5 fever and is quite sick but is responding to the Tamiflu.
It is said that folks over the age of 45 have some resistance to H1N1 but your parents are at high risk and so they should get the vaccine and if it is available where you are, and the vaccine is in short supply, you should get it also.