LimaVictor wrote:
we have lived together on a 70ft motorboat with 2-4 other people (and a dog) for at least a week, sometimes 2, every year since we've met, so the idea of being confined to small living quarters and maintaining a fully self sufficient home is not completely foreign to us.
I do not think you are crazy, however, there is a big difference between living on a 70ft boat vs a 25ft Motorhome built on a Sprinter chassis.  With 3 medium size, active dogs, I don't think it would be comfortable at all.  As has been mentioned, a lot of campgrounds that allow pets (that we have been to) have a 2 pet limit.
Sprinter chassis based motorhomes do not offer a lot of empty space.  Where would 3 medium size dogs sleep?  Where would the baby sleep?  You are talking about living in it for a year.  If you plan to let the baby sleep with you, plan to have the baby sleep with you for the next 10 years.  It is a tough habit to break.
We are a family of 4 (2 adults, 2 teens) with a 32' Class C that has 2 slides and a bunk house. We live in it 4 - 5 months in the summer and it is too small for us.  A week long camping trip, no problem.  When we live in it long term, it is just too small.  If you went without the dogs, I think it would be much more doable.
-Michael