If you put the material in online storage like Dropbox, you're using up your disk space allowance, which may or may not be a problem depending on how much disk space you have (if not immediately then it may become a problem down the line).
If the material is 'static' (ie not regularly updated) and only needs to be shared with the group once, I would use Wetransfer.com to send it to them - you just have to input the list of their email addresses and upload the material, and they will be sent a link to download it. The free version of Wetransfer has a 2GB limit but that sounds like it should be enough for your needs.
I also like fuaran's youtube suggestion. You can make a private channel on youtube if you don't want the material to be publicly available.