It feels daunting as you think that you won't have anything in common with your colleagues but the conversations are exactly the same as pre-children except your priorities have changed. I was fearful that technology had moved on but with the aid of google most questions could be answered and surprisingly I knew more than I thought.
I felt the obligation to work twice as hard to justify my part time role but you genuinely don't have to do that. As long as mentally you are engaged fully when present at work then you shouldn't feel guilty scooting off at the end of your working day.
Getting back to the practicalities of working part time I'd invest in a slow cooker as there is nothing more satisfying as working and then coming home to a house filled with cooking smells - you will deserve to be smug at this point.
I found that breaking down the housework to a few jobs each day meant that when I was at home I wasn't spending all my free time doing housework and I still had time to spend quality time with the children. Antibacterial wipes in the bathroom means that you can wipe the sink, toilet or bath around whilst waiting for the bath to fill.
If you split the washing between lights in the basket and darks in the washing machine and vice versa the washing machine is always ready to be turned on and the washing machine never looks overfilled. Before putting the washing machine on I'd iron the previous batch of washing, this kept the task small and easier to fit into my working day.
Good idea to have a back up plan for childcare. Make sure that Dad also participates in childcare as they are his children too, then you won't feel that you are solely responsible for childcare if the children/care givers are poorly, etc..
When catching up with phone calls at home I'd put an old sock on my free hand and whilst talking on the phone (loudspeaker) I'd dust - dust free house, dutiful daughter/friend and a little bit of exercise too.
Family planners are key to working and raising a family, nothing happens unless it is on the planner! Make sure that you plan some 'me time' on the planner too, doesn't have to be much but if it's on the planner then it has to happen.
Good luck in the new job and managing to achieve a good home/work balance.