Thank you for your post.
You can think of FileMaker Go (for the iPad) as a FileMaker Pro client. They will be able to access a hosted file via 3g or Wi-Fi, very similarly to how users on laptops are accessing the hosted files. You can set up additional user accounts and passwords for the iPad users.
You can share a database across the network with nine other users simultaneously. If you plan to have more than nine users simultaneously, then you will need FileMaker Server to host the files, and all users on laptops would need FileMaker Pro and all users on iPad/iPhone would need FileMaker Go.
Let me know if you need additional clarification.