We have $200k sitting in an e-trade IRA, for retirement. We just rolled the money into this IRA, and the funds are unallocated. We're pretty risk-sensitive, but this money will be untouched for decades, so we'd like it to do at least a little work, but without too much risk of loss.

Suffice it to say we know next to nothing about investment. Is there a good rule of thumb or general advice as to where the IRA funds should be allocated that would minimize risk, but still bring a little bit of a return?