Hi!
Have just started my Master's - am about a month and a half in - with a 3 1/2 year old and a 1 1/2 year old. DC's are in nursery 2 1/2 days a week and I have classes 3 afternoons a week. The other 2 mornings I use for studying.
It is tough! But yes, if you are organised then you can do it. Also, I've found I have to prioritise. DH doesn't cook beyond heating a frozen pizza, so I have had to accept that the DC's will be eating pizza / pasta and ready sauce etc on the evenings that he collects them. In fact I have just had to accept that our diet has been reduced to 50% convenience for this year - not ideal (have always been a big cook) but this is a 1 year project and it's worth it.
Do you have an OH and how flexible is your OH in terms of duties with the children etc? My DH has to fetch the children on certain days, and then there are occasions when classes get moved (today for example, he is having to work from home because my Tuesday class was moved to this afternoon for this week and the dc's don't go to nursery on a Thursday).
I did have grand plans to study in the evening once the dc's are asleep, but we also moved country for me to do this and they have been very unsettled. So I shifted my day round a bit so I often go to bed the same time as them (round about 8pm at the moment) and then wake up at 5am to study a few hours before they wake. (This doesn't always happen, sometimes I wake up at 11pm all refreshed to do stuff for a few hours and then of course am knackered the next morning - we're still trying to find our rhythm!)
And yes, it's hard switching between days of being a full-time mum and days of being a full-time student. And it can also be hard to watch everyone troop off for a pint at the end of a 4 hour afternoon lecture on a Friday and you have to rush off to pick up children, get them home, cook supper, bathtime, bedtime etc (me, bitter? Nah...!)
Good luck - I do feel at times as though I am holding together a skyscraper in a tornado with blu tac, but hopefully it will all be worth it in the end!