It is surprisingly easy to do. There are several patterns, so it may be useful to learn them all.
Show all files in that directory
vim -p *.*
The -p means open in a tab. You can use wildcards to specify that any file will match. This usage was not possible with tabe. I am looking for another way.
Show all files under that directory
vim -p */*
Show all files and directories under that directory
vim -p *