Congrats! Sweet looking nursery! I'd be a bit weary about the crib being so close to the tank though. Especially if the kid throws bottles/hard toys out of there, or like some I've been told about that do back flips out of the cribs (my sister). But I hope you don't have any problems.
Since it looks like a wooden hood it might be easier to install some sort of locking device. A topic I'd be interested in: How to install locks on fish tanks.
I think it was around age 2 that my daughter started messing with tanks. My son never did, my daughter would push chairs up to the tanks. Probably didn't help that they are usually in the dinning room. lol She's overfed several times and very slick about it, even putting the food container back where I keep it. Things she's dumped into tanks, flake food, aquatic fert tabs, seasoning salt, oddly the only fatal one was the sinking shrimp pellets. I didn't know what was going on at first, for several days she was giving them to the fish waiting until I was out of the room for a min. If something dose get in the tank, water change asap has saved what I thought should have been bad. And the seasoning salt just happened to be a heavily planted tank.