Google "Campaign for a Commercial-Free Childhood" or TRUCE (Teachers Resisting Unhealthy Children's Entertainment); these are both valuable resources I have guided my preschool families to. (one more at end of this post.)
I can say, from years of experience as a preschool teacher and nanny, that media greatly influences children's play--and not for the better, in my opinion. I ask the parents to refrain from sending the children to school in 'character' clothing or bags, lunchboxes, toys etc. I have discovered that, when we even have a soundtrack playing, the lunchtime conversation goes from imaginative, interesting topics and recollections to a pretty dumbed-down recounting of the story of the movie. The kids at some preschools I worked at would wear their Ninja turtlesPower Rangers/Pokeman or Disney Princess apparel and then want to play out these extremely limited and prescripted roles. Much of this play is either violent or sexually coy, and brings out the worst in our children.
For me, the worst of it is that much of television is one-way and non-interactive. (Not computer interactive, but human-interactive). My only exception is Mr. Rogers, who addresses his viewers as "television neighbors" and asks open-ended questions about feelings, doing 'right' and discusses options for dealing with hard situations. (We do watch this with our son, side by side, and have a limited library of these dvds.)
Also concerning is that institutions like Sesame Street have commercialized their characters to become *marketing messengers*. I'm still furious with CTW (Children's Television Workshop) for allowing the mass licensing and merchandising of its characters. This actually CREATES a child consumer who wants items not for their worth or value, but because they experience an emotional connection to the Muppet or character shilling the product. I believe Jim Henson is spinning in his grave at the Disney-esque marketing mess CTW has become.
Children tend to have no lines when it comes to distinguishing fantasy from reality. They don't understand that those things they see on television may not be true. My husband was a kid when the George Reeves "Superman" television show aired--at four or five he *actually ran through a plate glass window*, thinking he's be like Superman. He still has the scars. We adults take for granted our ability to differentiate between fantasy and reality--children don't have this. They don't even understand sarcasm.
Topics are also out of the realm of what is relatable to a child. One example would be "Arthur". Many parents let their toddlers watch this show as it falls under the umbrella of "children's programming", but it models terrible situations: the children are mean to each other, girls are put down, boys are bullies or nerds--there's so much toxic stereotyping in this show. Yes, there's always a resolution, but our young children do not have the critical thinking skills to process this information/situations in ways that are remotely helpful. Instead, they learn how to be rude to each other. This would be suitable for much older children who might relate to this sort of dynamic, and side-by-side viewing would provide parents opportunities to combat negative role-models.
The last thing I'm going to say is this: I've found that children who spend more time with television seem less-cooperative and less able to play in a constructive/imaginative way than those who aren't entertained in this way as often. My son is included in this: even as careful as we are with media, I can tell when we've allowed "too much" television, because he's less cooperative. Perhaps it's because he 'connects' to tv for the entertainment and pseudo attention instead of us, his parents. He begins to get a bit whiny for it, less able to keep himself busy and happy.
And I have to go now, because he's asking for me. But overall, I'd say you are trusting some strong instincts in protecting your child. Also, check out the new movie Play, Again. (You can google Play Again Ground Productions). This is a well-done documentary of the effects of media and it's consequence: children growing up without a connection to nature. Recommended viewing for anyone who cares about raising brighter, more socially and emotionally intelligent citizens. Best wishes, brave woman!:)