aglo, I was a single mom for many years, my first husband passed away also. And I too worried about the same things you are now worried about. I too, put my two older boys in sports etc. and I noticed that they really appreicated the male teachers more than the females at school. If feel that espeically boys, need strong, good male models. But it was so hard finding anyone that would fit the bill. I was in a strange country with no male relatives around and only just finding my way around myself.
But word of caution though, don't just get together with someone just to get a male figure in your kids life, it is not that easy finding someone who will love your children as you love them.