We did DD's 2nd birthday party yesterday. We held it out our house from 2-5 (some good friends stayed a little later). We chose that time so she could nap at home, and continue to do so even after the party started, and also I didn't have to provide a full meal. We had heavy apps and cake and ice cream.
I like having 4pm Sunday parties if it's mostly adults. Snack & mingle, eat, presents, cake. By 7 everyone is ready to go home and get ready for the week. If I had an early Saturday party, no one would ever leave and I'd have to hide outside with a bottle of scotch, funnel and multiple cigarettes stuffed in my mouth.
If you're not trying to cater around naps, 1pm is fine. For anything that doesn't fall over a "standard" meal time, it's nice to include what you expect... if you're planning to serve lunch, let people know. If it's just going to be cake and ice cream, let people know that too. There's all kinds of "cute" ways of saying these things.. but it lets your guests know what to prepare for.
Re: Boring Birthday Q?