So I'm new here, but I was on OG and have a few harvests under my belt... I had a similar starting setup as yours, and with adequate airflow in your room, you'll have all the CO2 you need. You won't leave anything on the table by not using it.

Now if you're just DYING to add CO2 anyway, you can do what I did: brew hooch in the grow room. Seriously google "fruit juice alcohol brewing" and you'll find a device that let's you brew OJ hooch in a Pepsi bottle. It emits CO2 naturally. Everybody wins!