"is this the best and safest plan for long term growth."
As to the three mutual funds plan, if you put a low, a moderate, and a conservate together you end up with the whole stock market. You can save on expenses by buying a market index fund like the Russel 3000 or vanguard total market index.
A more important decision is how much you will but into catagories like stocks, US bonds, international bonds, cash and possibly at some point in the future gold and foreign currencies.
"Is ING direct a good place to invest?"
I suggest you look at expenses. If I read it right the expenses at ACBLX are 2% and there might be a front load.
http://finance.yahoo.com/q/pr?s=ACBLX
Unless you have a good reason for doing it I suggest you avoid expenses of greater than 1%. Try vanguard.com or ishares.com for low expense funds. Possibly PIMCO total return fund (if you want to pay for active management).