Maybe you want to take some of my blinkenlight experiments for your class. Hardware requirements are very low and the difficulty range is from easy to advanced. You do not need the shields you could also create the setup with breadboards. However you could also use the kits which are cheaper and do some SMD soldering practice. However I have no clue if soldering is fine with 8 year old boys. I learned it at the age of 12 
SMD soldering should be easier for them then for us because they have most probably much sharper eye sight.