I'm not a single mom, and I only have one child, but this is a question I'm sure many of us have had to consider in some way. A few thoughts I've considered on the way:
- only you can decide what your priorities are, there is no single perfect solution. I need way more sleep and down time than many other people, while others again might find my schedule incredibly stressful.
- often you need a little perspective to really see how you use your time, and consider if that's in synch with the way you want it. If this is going to be your situation for a while, I'd really recommend (i.e. this worked for me) taking a few hours at some point to "time budget" a regular week, writing down how much time you actually have and use for work, sleeping, training, being with your kids.
- family and kids past the baby stage rarely "demand" time, the way work and training with a group do. It's very easy to let time with your family by default be the time you don't "have to" do something else, which means that that time is vulnerable.
- there is nothing wrong with letting other people help you or join in in raising your kids, and there is great value in teaching your kids to be self-sufficient. If you are unsure of your motives for leaving them alone, maybe consider if you would have done so even if you didn't have a training session to go to, purely for the benefit of learning independence.
- yes, kids are top priority, but they don't have to have first priority all the time. Generally speaking, kids are adaptable, and if they feel that they have your love, attention and focus in life, the actual number of hours you see them isn't that important.
- give a little thought to where you will be and how old your kids will be in a few years. I suddenly realized that I right now have a bright, chatty, affectionate 13-yr.old, and in maybe just 1 or 2 years I could have a sullen teenager who will barely talk to me, let along listen to me or spend time with me.
Make of this what you will 
PS. I didn't answer your question at all, I see... Personally I think age 10-11 is old enough to fix breakfast and get to school alone once a week, no problem. They may need some help getting started, but they'll be so proud of managing it.
Last edited by lph; 02-28-2011 at 01:57 AM.
Winter riding is much less about badassery and much more about bundle-uppery. - malkin
1995 Kona Cinder Cone commuterFrankenbike/Selle Italia SLR Lady Gel Flow
2008 white Nakamura Summit Custom mtb/Terry Falcon X
2000 Schwinn Fastback Comp road bike/Specialized Jett