I would keep them separate. Aside from the warnings on quail catching chicken diseases, I would think the larger chicken chicks would bully the tiny quail chicks around the heater, water, and food. I will soon be in the same predicament. I am hatching 75 chicken eggs for a friend. I keep half of what hatches. I also have a small batch of quail eggs going. They are due to hatch within days of each other. My brooder is 6'x8' and I have a partition to keep the birds apart. I usually don't keep chickens, so my brooder usually holds upwards of 500 quail chicks. I sell most within the first week and keep the rest for myself. Last batch I had 378 chicks hatch and sold every single one before the weeks end. Sometimes it just works out!
Chicken-Farmer