How to share an album with multiple folders?

I think you've got the terminology the wrong way round....Albums cannot contain Folders, but Folders CAN contain Albums. So I assume what you really want to do is share a folder which contains 3 albums, yes? At this time, that's not possible, you have to share the albums individually. You could consider using the Gallery option in Lr Web (i.e. add the albums to your Gallery and share that one link), but you can only have one active Gallery.