If you want people to dance, IME you need at least someone to man the iPod, if not an actual DJ. Got any mates who you could bribe to do an hour or so?
Unattended playlists are fine but you need someone to judge the mood and match the next track to how it's going IYSWIM. If you have an iPad there are a few apps that allow you to cue up music and play them with no gaps in between.
Just after a bit of advice for my 40th party. Have booked an area in a swanky hotel not far from where we live. Am envisaging around 50 (perhaps up to 60) people attending, a mixture of family and friends (new and old). I don't want to do a sit-down dinner or buffet as feels a bit stuffy, so am doing canapes and a champagne reception. The evening will finish at 1am.
My question is should I hire a DJ or just create own playlist on the ipod (or DJ friend create for me)? My friends are the type that are definitely up for a bit of a boogie/late night and hopefully lots of them will be staying over in the hotel. But I just think that hiring a DJ for 50 to 60 people is a bit overkill? It's hardly gonna be a riot on the dance floor! Money isn't a problem but just don't want to get the right balance.