Sure they can!  Unschooling at its heart is about providing your children with what they need to learn and to love learning.  If that means using curriculum then do it.  About a year into this homeschooling journey it became obvious that what our little girl really wanted was someone to hold her hand and lead her step by step through a process.  Pre-set curriculum is great for this and as long as it works for her (now them) then it works for me.  It should be noted that all the seatwork we do consumes at most 2-3 hours of our day (and usually much less).  The rest of the time is allotted to spending time together as a family (working and playing) and free exploration.

If you’re interested in specific curriculum information check out these posts:

Curriculum?? (from 2008 ~ includes lots of our favorite web links)

How We Workbox ~ Part 6 (Inside the Box) 2011-2012