I agree with JamieLeeCurtis that having a partner working from home is tough, and not the convenience-fest that others might imagine.
It's always been this way for us and it is very hard to know, when DC are challenging and the jobs are piling up faster than you can deal with them, that upstairs sits an adult listening to iPlayer and having a cup of tea.
Somthing like bringing in the food shopping while looking after toddlers is so hard to do when you know that an extra pair of hands is just up the stairs.
However, it is crucial that the person who is on childcare duty behaves largely as if the other were simply not there. The other person is at work. Distractions lead to slower productivity, which in the end means longer working hours, which means the situation drags on and on...
It is helpful if the homeworker keeps set hours of work. That way the person doing the childcare knows when it is okay to start handing over, letting kids go upstairs, etc.
It also avoids the homeworker sneaking off to their desk at random times to visit Mumsnet under the noble guise of "work" 
Try telling your partner that, if you can be completely free from distraction, you can get whatever it is finished by, say, 4:30pm. However, if you are disturbed all the time, he'll be stuck with DC until 6pm!