Yup, you'll need someplace to put the babies between the time they go outside (6-8 weeks usually) and 12 weeks or so. If you had a bigger coop/henhouse, you could section off part of it with wire fencing, so they older ones can see the youngsters but not bother them. That is what we plan to do with our chicks.
If you haven't already bought the dog house, I'd hold out for something bigger. Ideally you want at least 20 square feet of useable floor space for 5 hens (not counting where the food/water/nest box/droppings board are) so that's about 5 x 4. Personally I would go a little bigger, especially if they aren't going to be out free ranging all the time.
Your enclosed run, assuming you have one, should give them 10 sq feet each or 50 sf total. Again, bigger is better to stave off pecking issues. If you can let them out to range in your yard, that's great, but you may have predator issues.
Some people have converted playhouses, but again it needs to be big enough. We used a corner of our garage (see coop page in my signature line).
Good luck!
