Yes, using both agreements shouldn't be a problem. The work-for-hire agreement will be what you use to show transfer of ownership with the Copyright Office. Since the CO is only an office of record, they don't really care what your revenue sharing %s are. On a project like this, it would be best to consult with a lawyer to review each agreement to make sure that your ownership and revenue sharing terms are clearly outlined in both agreements to avoid future dispute.
DISCLAIMER: Please note that this answer does not constitute legal advice and does not create an attorney-client relationship with myself or Saku Collins, PLLC. This answer should not be relied on since each situation is fact specific, and a lawyer should always be sought out directly when a legal question arises.
Mr. Saku is spot on. I write only to add that you need to query amazon.com for "entertainment law" and buy a few books on the subject before you enter into a collaboration to create a television show. There is no excuse for not doing your homework. Better still, of course, is to hire an attorney to set up the collaboration properly (you could unknowingly enter into a default partnership or joint venture).
If you go it alone, you should consider recording with the Copyright Office the agreement that assigns to you (you mean your production company, right?) the copyright interest that your collaborators have in the scripts -- and then register the copyright in the scripts once each is written. See http://tr.im/qlEr and http://tr.im/qlEQ .
Defining the copyright transfer document a "work for hire" agreement is really a misnomer -- the document is BOTH a work for hire agreement and an "assignment agreement." That document will be very important. Do not rely on one you find on the internet. Have an attorney draft one or, at least, review the one that you cobble together. Good luck.
The other responses provided you with good advice, and you're very smart to put things in writing with your collaborators to avoid disputes later on. There's nothing wrong with you being 100% copyright owner under a work for hire agreement and also sharing the profits with your collaborators. I'd add that these two agreements give you the ability to define income shares as well as attribution of credit to your collaborators, and to accord credit separately for story creation and writing. Further, since you're using the WGA Collaboration Agreement, you can also use the WGA's registration service as well as the U.S. Copyright Office's registration service (see my Legal Guides linked below).
Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.