I have chopped and changed my work arrangements since having kids and have had no problems what so ever. They have been very accommodating. I have always asked for what I wanted and got it as in days and hours.
I have been full time, pretend part time (1 day off), 3days and now currently two days and will increase to 3 when DD starts school in 2yrs.

My only problem is I am wanting to change rolls and would need to go full time for most of the rolls, so I am a little stuck with job possibilities. That's OK for now, willing to stick it out and move agencies if I need to.
I work in a government dept.