for the 50mm, it really depends what you want to shoot... if it's close up of items, 1.8-2.8 is really great to achieve a shallow DOF and allow your subject to be in focus. However, for portraiture, i find that 2.8 onwards is just nice (depends on the lighting available and your ISO settings)

I've just been blessed with a baby boy 2 weeks ago and the 50mm's all i've been using as it's very fast and can capture the 'cute' moments. you'd be surprised how many expressions a baby can make! great lens all around in all honesty- good price too.