My last boyfriend had a 2 year old daughter, which at first I didn't think would bother me, but in the end it did. When he kept cancelling on me to look after her, it got very annoying.
People who have kids will (rightly) always put them first, before anyone or anything. You have to be a super-human partner to be able to deal with this though; and unless you're madly in love with someone and couldn't bear to be without them, it's really not worth the trouble.
But, there's no harm in a few dates... but I'd strongly advise against anything serious, just because it gets too tricksy. Unless you, unlike me, can cope with always being second best.