I work very similar hours (though 30 mins for lunch and so start work at 8:15, and finish at 12:45 on Friday) and have a similar length commute, and I have a 10 year old. BTW my whole office does these hours. The previous job I did was evenly spread over 5 days.
I find Mon-Thursday to be very long days, it took me 2 months to really get into the swing of things. Fridays are great, yes, but I often resent 'only spending 4.5 hours' for over an hour's commute. On Fridays, I tend to catch up with paper work and plan the next weeks work, rather than doing 'real' work if you see what I mean.
Pluses are - I can organise things for Friday afternoons, such as hair, dental and other appointments while DD is still in school. Or just have some me time. Oh, and I pick DD up from school on Friday afternoons.
Minuses are - not long enough for lunch really, and work are not very flexible about this. My leave allocation is in days and half days, and not hours, so that if I take Friday off on leave, I have to use a whole day! DD has to go into before and after school care and DH does all the school runs except Friday afternoon.
I've been doing this for 9 months now. I really like not working Friday afternoons, but the rest of the week is very tiring, and the biggest issue of all is that I'm not getting as much 1-1 time with DD as DH does and its affecting our relationship (as in mine and DD's).