In deaf education, we often do "listening walks". It's simply a walk around where we wait for the kids to hear something and locate the sound. We will then talk about it. If the kids aren't hearing something, we'll direct their attention to it. It's a great way for kids to hear an environmental noise and learn, first hand, what that sound means (car horn honking = car is coming) and how to react (stop moving). When I taught at Sound Start: A school for the deaf and hard of hearing, we would often take listening walks on lawn day. The maintenance men were very sweet to make sure to come close enough to us so that the kids could see what they were doing while listening to the sound.
While listening walks are wonderful, let's not forget our other four senses: touch, taste, sight, smell. Take a walk with your kids (it doesn't matter the age) and have them find things they could touch and describe how it feels. If they don't have the words for it, give them the language by saying, "that feels rough." Let your kids find things they can hear (a lawn mower) and explain what it is, what it does, if it's loud or soft, etc. Taste is one that may be hard to do unless you "plant" a treat for the kids to try. :o) Let the kids find something they see - maybe you're focusing on a certain color or shape that day. Have the kids describe that object as best they can. Give them the language that they don't have to fill in the gaps. Let the kids smell things and describe their smell - good or bad. It may be funny to do the walk on garbage day and see if they notice the garbage smells. Let the kids take the lead as much as possible. If your child is a pre-talker, then watch him/her. When he/she is focused on something, then describe it to him/her. Your pre-talker may not be able to tell you what he/she sees, hears, smells, etc, but where he/she is focusing will tell you what his/her little brain is trying to learn about.
If your child works on articulation, then make sure to find things that have your child's sound or listen to your child's sound in conversation.
If your child is working on listening comprehension, then take an "I spy" walk. Say something like: "I spy a car", "I spy something that smells yucky", "I spy something that is blue and says vroom", "I spy something that has four legs and a tail", etc.
If your child is working on fluency, then work on his/her "smooth speech" while on the walk.