Luckily, at their ages, homeschooling them isn’t nearly as complicated. You can be as structured or unstructured as you want – from buying a whole curriculum as people have suggested, to getting a few workbooks and plowing through them. You won’t necessarily have to have a “school day” as long as traditional school – it is quite likely that you will be able to get your small “class” through all the work by lunchtime if you want to.
I would suggest writing down your educational goals for the year. First off, why are you homeschooling? In what ways do you think they can develop this year? You can put in this category your social and behavioral goals: for instance, learning to sit still, to follow the daily schedule, to work well in groups, what-have-you. Then your goals for every subject – fluent reading, math up to X level in a book (or up to additon and subtraction, etc.), a lot of field trips for science and history …
When you know where you want to go and how much you want to achieve within a year, you’ll have an easier time making all the decisions that go along with that, like curricula or schedules.
Do you know any homeschooling families in your area? Do a little research and see if you can find some. Their advice and cooperation will be invaluable as you try to homeschool.
And, of course, know your laws. A Google search should tell you everything you need to know about state educational requirements. In many states, education is not compulsory until the age of eight – so you can homeschool with no extra requirements until then. This might not be the case, though, so do check.