hi A., i never used a complete box curriculum, but did grab bits and pieces. i hear great things about math-u-see. we started homeschooling later, and used saxon (which no one loved but actually worked best for my kids' learning styles) and later Uncle Dan's Algebra.
if i WERE to use a boxed curriculum for a 1st grader i'd have 100% gone with Oak Meadow or Clonlara. there are probably a lot more out there now, but we were in the early years of the internet as a resource when homeschooling.
as for the rest of it, i'd try not to overly compartmentalize your homeschooling. one of the loveliest things about is that you DON'T have to 'limit times for learning.' homeschooling and parenting become inextricably intertwined.
organization is important, though. i kept ongoing files of their work, and a journal (spiral notebook) of quickly jotted chronological notes of stuff the BOE wanted see, such as field trips or specialty activities like helping estimate the amount of fencing needed for a field, the cost, and the work itself. all of that too will be useful down the road when creating transcripts for college admissions.
i let my kids organize their own time to a great degree. i set up weekly outlines of what i wanted done in that week, and they got to pick how to meet those goals. sometimes they'd knock it all out the first day in a marathon. sometimes they'd wait til the last minute, sometimes they enjoyed parceling it out day by day. a little fellow like yours will need more oversight, but start to practice letting him expand and contract his own schedule. it's incredibly empowering, and something few children get to experience.
i didn't unschool, more because of my own fears than anything else, but got as close as i could bring myself.
the longer you homeschool, the less you'll look for curricula. once you've got a firm handle on your kid's learning style, his strengths to be fostered and his weak spots to give extra support, you'll find it easier and more helpful to simply create your own. but starting out it's great to have it in a package.
good luck! you're going to love it.
khairete
S.