Day time TV and the poor quality programmes aimed at children are not good for their language and reading skills and general development. I never let my children watch anything before 3.30.
There are some good alternatives. Story CDs are brilliant, especially when unabridged, and they build up concentration, listening, vocabulary and grammar skills. The adult also gets to choose the CDs and thereby controls the input (you can, for example, avoid, 'Teletubby' type non-language based programmes). There are also CDs that teach numbers, letters and tables by songs and chanting.
You can offer picture books to two year olds as it is never too early to kick start their pre-reading abilities and habits.
DVDs with children's narratives are better than 'putting the telly on' as, again, the adult can control what is watched and ensure it is of a high quality.
Libraries offer children's CDs and DVDs at minimal cost and charity shops are full of such material at bargain prices.