How to export all projects from Aperture?
Select the material you want to export and File -> Export -> Version.

This will give you the Export dialogue. Look at it closely as it has a lot of options.

Somethings are quite obvious: Where to export to, for instance. But note the others:

Export Preset: This determines the size (length x breadth), file format and compression applied to the image on export. (So, full-size, tiff/jpeg and so on). Note the option at the bottom of the dropdown to Edit - that allows you to create your own Export preset depending you your requirements.

Next note the SubFolder Format. That's what allows you to design a naming scheme for the exported projects. There are presets there, and again, using the Edit option you can devise your own.

I note that you then plan to delete the projects from Aperture. Why? Not sure you've grasped the point and purpose of the app if that's what you're doing...