I hope you are planning to stop at the dam for a tour. I toured as a child and it had a strong impact on me. The tour requires a great deal of walking, so take hiking boots!
RE: Packing don't forget your address book, spare change for vending machines and band-aids/first aid kit for little emergencies. Also prescription medications for non-daily items such as (emergency inhalers, allergy meds, nitroglycerin tablets), whichever is applicable. Have a great trip but don't forget the hats and sunblock - Nevada is hot!