OK, so for the first question, that really depends on you. My mom went through the school system and got public school books for me until middle school. Back then homeschooling was considered taboo and the principal at the middle school gave her a hard time so she started choosing her own curriculum which was Bob Jones University books. I'm sure there are so many more options for curriculum's now, though.
As for staying focused, since he is in preschool I would do short days and maybe even just a short lessen at a time, then when he starts getting wild, move on to something fun for a while. Try to find fun games that are still interactive and good for learning. There are lots of free sites that have fun little learning games on them. (ABC mouse did have a free month, not sure if they still do.)
As for scheduling, since he's so young, I'd just try to get in a typical routine. Waking up at certain times, working on learning at a certain time, lunch, etc. As he gets older, if you choose to still homeschool, make sure you plan your schedules in advance. My mom always sat down and planned out all our lessens for the whole year, numbers of pages that we were going to be doing in each book every day. That way, as I got older, I could get her book and look up what we needed to do next and go on without her having to sit there with me every second. I could also get done with my work super fast some days and have the whole rest of the day to do as I pleased.
I say google free sites for preschoolers, even print some workbooks out.
