If you are going to set it and forget it, just build a nice balanced portfolio of funds. Check out the funds fees online as well.
Fidelity also should at least have an 800# you can call to get some ideas as well. You don't have to follow their advice, but at least see what they recommend. There could also be a local broker/office you could contact. They are getting paid handsomely for that, you might as well use it.
Make sure to 'xray' the funds to be sure you don't have a ton of overlap. In other words, you don't want to be diversified in 5 funds only to find out the funds all own the same basic stocks.