A grassy field is my favorite type of location. In Central Oregon we have tall yellow grass and softer green grass to choose from. I love photographing through the tall grass as well as having plenty of space for kids to run around and play.
Pros: Easy to get to you. Easy to play in. Great for kids of all ages.
Cons: Some grass can have stickers in them that will get caught in your clothes.
Props to bring: Blanket, couch, chairs, bubbles, bikes, signs, etc. Pretty much any props can work great at this location (which is another reason why I love the grassy field).
Colors to avoid wearing: Creams are not great for this location since they blend in too much to the grass. If you want to wear cream, wear it as an accent or bring a jacket or scarf to create contrast that separates you from the backdrop.