As a mom of grown up kids, I would still emphasize it is important to "schedule" your special time to do activities you want to do. My son was like your three year old. If I couldn't see him, I ran because he was probably into something. (one time, he even cut the cat's whiskers off!!!!). They do need constant supervision. (mine didn't nap very well either......)
One thing that saved my life while I had kids at home was a babysitting cooperative. We had a group of about 10 moms with prek age kids and took turns babysitting for each other. If you sat kids, you earned points and if you left kids you lost points. It was a very "fair" arrangement and gave me an opportunity to do errands and sometimes even just going out to lunch without paying for babysitting.
If that kind of an arrangement is not possible, think about the people you know with children. Find another mom who would be willing to trade kids for one morning a week. Just imagine a whole morning to quilt or scrapbook without the worry of your kids!
And, as it has been mentioned before, Dad needs to do his duty. Set up specific times for yourself when Dad can watch the kids. (even if that means sewing at someone else's house). Having a specific time really will help you to plan what you want to do (and sometimes that may mean watching a favorite movie with no interuption or taking a nap!) I might add that it is just as important to have "couple" time without the kids. You just have no idea how busy you are raising kids right now. You will reflect on it when they are grown and wonder how in the world you did it all.
Let us know how everything is going. We really care and want to see you in the mood to sew! :lol: