VLM training - 5 sessions 3 days????

I would appreciate some advice. Just found out I have secured a place for the VLM. I have completed 2 previous marathons including VLM '11 and have a PB of 3hr 20 min. Obviously I would like to better this in April but with my third baby due in January I have made a commitment to my wife to only train 3 days per week. I have used the commute to work for training during my previous 2 marathon training cycles and often get up at 5.30am once a week to run. I am looking for advice on 5 sessions 3 days per week. My plan would be for a LSR on the weekend and then 2 days where I train early morning before work and again after work. I was thinking of 8-12 miles early at a slower pace and tempo/fartlek runs later in the day. I will aim for 45-60 miles per week I am sure some weeks I will be able to spread the sessions but would love any advice or pointers from anyone who has experienced a similar approach. Thanks Marc