Another reason to vote early: if there's a problem with your vote, you have more time to make sure it gets resolved. When I was 18 I went to vote in my first election, a city council race. I'd done my research and was excited to be voting for the first time. However, my family's home had been recently annexed and the computer records hadn't been updated. They made me vote provisionally. I called the county official in charge of the election and explained the situation, and asked that they be sure to check the updated records so my vote would be counted. Turned out that the election administrator (whose name I remember to this day) felt no need to actually check the records, and settled for the outdated computerized records. He threw out my vote. He later admitted that I should have been able to vote, but told the editor at the local paper that it was only three votes (mine and my parents') that got thrown out and therefore didn't really impact the outcome of the election. He never apologized or expressed any regret, nor did his supervisors when I contacted them hoping for some sort of action. It was a non-issue as far as anyone with the county was concerned. I am still appalled at the lack of due diligence regarding my vote, and the complete lack of concern the official and his office showed after the fact. If I recall correctly, city elections were generally getting maybe 4-5% voter turnout, and there I was 18 years old, having made sure I knew who I was voting for and why, and being told that my discarded vote didn't matter anyway. What a way to encourage young voters! Instead of letting it discourage me, I decided that will be the one and only time I miss an election. And I vote early, because if that ever happens again I will be at the official's office and in his face until my vote gets counted.
Also second what Texsquatch said -- take the kids! My kids go with me every time I vote, and on our way we talk about what voting is and why it's important. I remember going with my mom when she voted, and I even remember her hosting MUD elections in our home and volunteering at polling places.
A nice election volunteer sat down with the older two (6 and 4) while we were in line and showed them how to use the sample voting machine (I think they got to choose among candidates for the purple, blue, and silver parties). They thought it was pretty cool. My only objection is that she taught them to vote a straight-party ticket. 
Personally, even if I'm voting straight party I'd rather select each candidate individually. It's probably silly, but I like the feeling that I've selected each individual candidate I'm voting for. And a friend who regularly volunteers as an election judge has told me that usually when they have problems with the machines, it's on straight-party votes rather than individual ones.