Greetings!
I think it's wonderful that your son is interested in bird watching.
I have three children and one of those is 5 also. And in fact he loves to bird watch. Our family is very much interested in nature.
Making the pinecone feeders and making homemade suet are great ideas.. however I would encourage you to use ingred without additives etc. For instance.. use natural peanut butter instead of the processed kind made with all the sugar. In the wild birds eat sugars from berries and fruits but not our refined sugars. The peanut butter does offer a protein source.
Things that even a five year can learn is that different birds have different eating habits. For example: Cardinals are fruitivoirs eat seeds and berries and will eat from a feeder and some on the ground. Blue Jays are omnivoires and will eat insects and berries etc so they will eat from the ground and the feeders and Robins are insectovoirs so they will eat on the ground. Of course in cold weather if food is scarce you may see a slight crossing of feeding habits.
Not all birds eat seed. Do a bit of studying to figure out what type of birds you have in your area and what they like to eat and where. My son thinks this is fun. We watch the feeders pick out a bird and then look it up.
You might consider different types of feeding stations. Thistle is very popular among many birds but it is a bit expensive.
If you have a Wildbirds Unlimited in your area they may have some ideas.
Bird watching is a hobby that can last a lifetime and be a wonderful family activity.
You might also check your local 4H Clubs...sometimes they have info and ideas as well and a local Agricultultural Extension Agency. We have also bought pre cut bird houses and put them together and placed them in safe areas.
If you have cats in your area remember to place your feeders at least 6 ft above ground to keep the birds safe from harm.
Have fun!
Robin in NC
www.bunnyrabbits.org/southerncomfortrefuge/ 
I forgot to add that in the Spring and Summer not to forget your Hummingbirds. You can make a simple solution or buy some. Try to get the kind with less red or no coloring. 
