Yes it will be smelly at times and noisy but you will get so used to it you will filter most of it out.
Something I dont think has been mentioned is that when they take the calves off the cows they will make a din for quite a few hours/a day or two afterwards. If they are housed in a barn during the winter near the house you will smell them too
And yes there will be a bit of cow muck on the road if they are led past the house twice a day.
But I live in rural area surrounded by farms and you dont have to live next door to smell the muck spreading or hear the cows.
The peace and quiet compared to towns and cities and the landscape, nature (owls at night are magical to listen to) far outweigh the small niggles. And rural folks are very welcoming.
Its also great for the kids as long as you have gone over the basics of farm safety with them first, its not a play park. (am sure you know this but its a fascinating place for kids) Plus they may get jobs to do to help out if the farmer allows them and get a taste for farm life 
Talk to the farmers/farmers wife and ask questions, they wont be offended. Ask how much traffic (farm) to expect, do they bring the cows into a barn near you in winter, etc etc.
Just think of all the free food you can forage for! Brambles, hips, maybe rasps, sloes, elderflowers and berries...kids love it and making things with them our elderflower cordial is legendary 