Depends on your job, and also the age of your dcs.
"Fun" things, and assemblies thay want you to go to at school are much more likely to be on Fridays than other days, so that's a good day to have off with school age children. Training days are often on Mons and Fris too, so worth keeping in mind.
Some work places are more relaxed on a Friday - which you may want to be part of or may want to avoid
In my job, it's best to avoid working Mondays, as you use up a whole day's worth of annual leave every time there is a bank holiday, but you are only getting 3/5 of one in your holiday entitlement - which makes quite a difference over a year as 4 are always Mondays and 3 move around.
I used to work M/Tu/We and now work Tu/We/Th. I absolutely LOVE the fact that I don't have to have got everything done on Sunday evening - I can't believe what a difference it makes to my mood- didn't realise how depressing I found Sun evenings until they stopped!
Also, I find I get so much more done - be it housework, paperwork or whatever - around the house on a Monday, then I did on a Thursday.... I think you psychologically think it's the weekend, and slow down a bit.
If you want appts, or to go shopping, etc., then it's generally quieter on a Monday / Tuesday than at the end of the week which is a bonus.
Depends on your job though - some people (not me) find they cover the work better if they are there every other day - to my mind that suggests they are not really switching off and fully benefitting from the 4 days off work, but, they argue they are taken more seriously if their customers / clients don't get the message "She'll get back to you next week".