You can register for INBOUND even if you don't know yet who from your team will actually be attending.
If you want to buy passes before pricing goes up, you can register now and change the attendees later.
When You Register
Select however many tickets you want to purchase and enter your information under "Your Information" at the top of the order screen (go figure). A summary of the order will be sent to you at the email address you enter and that's all you'll need to transfer tickets to the right people later.
For each ticket, you can enter whatever info you want if you're not sure who'll be using it. Enter your name, your cat's, your favorite superhero's—whatever. Each ticket will need to have a unique email associated with it.
Pro tip: any text after a plus sign (+) in the first part of an email address will be ignored by your email server, so you can use that to create on-the-fly unique emails that'll all be delivered to your inbox. e.g. if your email is firstname.lastname@example.org, then you can use example+INBOUND1@acmecorp.com as one of the email addresses and the confirmation will show up in your normal inbox.
Once You Know Who's Attending
When you're ready to transfer your passes to the actual attendees, you can make the change by yourself in just a couple minutes. You can find instructions for transferring passes here.