This is my life. I work from home full time and I have a 5 year old who attends preschool for three hours in the morning three times per week. The rest of the time, she's at home with me. Here are things that have saved my tush and allowed me to get some work done. The biggest saving grace for me is that I have flexible work hours, do you have that option? Regardless, some ideas:
-- even if he doesn't nap, (neither does my daughter, really) we always have an hour rest time where she goes into her room and listens to a story book for an hour on her ipod. It gives her a little down time and me time to work.
-- get him a water color set and let him paint the bath tub. Heck, let him paint the tile around the bath tub too if you have it. It cleans up fast. This little project keeps my daughter busy for an hour. Sometimes more.
-- learning games on the computer. If you have another computer that you can sit next to yours, or if you have a laptop and can move it next to another computer in your house, you can get him hooked up with games on sesame street.org, or pbskids.org. I'm not a huge fan of letting my little one play video games a lot, but these are educational games that keep her busy while I'm busy. Plus, she really has learned a lot from them.
-- workbooks. You can get them at the dollar store and let him work on handwriting, numbers, reading, whatever. They're cheap, and you can sit him beside you while you're working at the table or desk and help him when he needs it.
-- have other friends over for play dates. At 4, my daughter was so much more independent and so were her friends. I could invite a friend of hers over who she plays well with and they'd disappear for hours. I'd keep my ears open for any issues, but generally, it kept her busy and happy and I was able to get work done.
-- send her to another friend's house for a play date. Do you have any stay at home mom friends? Usually, they're more than willing to allow you to do a kid swap. You send your son over to their house for a few hours one day, let their child come to your house for a few hours one day. My friends have been so incredibly helpful to me. Even if you can't swing taking their kid during the week while you're working, you could always repay them on a Saturday or with date night babysitting.
-- do any places around town offer day camps? Our Rec Center offers little day camps for kids where they can go play sports and hang with other kids for a few hours. You might look around and see what the options are. Usually they're very affordable.
-- Are there any mother's day out programs you can send him to?
--Are there any kid friendly places around your town that also have wifi? We have Going Bonkers here where I can take my daughter and a friend on a random weekday morning, they climb, and I work.
-- Make play doh with him and then let him play with it while you work. There are a lot of great play doh recipes online. Here's my favorite: http://www.easy-kids-recipes.com/play-dough-recipes.html
-- Here is a link to some other things you may think about too: http://www.sixsistersstuff.com/2012/01/101-fun-easy-and-c...
-- As a last ditch effort, I'll turn on a movie for her. But I don't like to do that. Though my daughter doesn't have any condition like ADHD, I feel like too much electronic stimulation makes her crazy.
-- Make a treasure hunt for him in the back yard. Go outside one evening after work when he's busy doing something else and take pictures all over the yard. Then, give him the pictures and a bucket and tell him to go explore and find each thing in the picture. Give him some sort of fun treat at the end when he's done. Tell him that if you help him, it doesn't count, so he needs to put on his thinking cap and really look for the pictured stick, leaf, rock, plant...whatever.
I'd suggest you sit down in the evening sometime and brainstorm a list of things for him to do for the 4 hours you need to work. When he gets home from school, he'll eat lunch, then make a good combination of creative and learning activities that he can do around the house. Take your computer out into the back yard and let him play outside for a little recess time under your supervision. Realize that he's 4 and playing by himself for 4 hours is hard for any kid, let alone one that young. If you can, take small breaks with him and run around or read him a book, etc. It'll be good for you to get up away from your computer too.
Hope this is helpful!
Good luck,
Hilary