Hi spinnerkop, I understand the concern!
They can easily be housed in containers with secure lids (these include glass or plastic containers or tubs), there are various options available, even ones that can be locked completely with something like a combination lock.
Another option is to house them in a secure container, at eye level, and out of reach in a cabinet with a lockable glass front. This way the glass-front serves as yet another backup.
There are actually many ways to secure them, but its all up to personal preference, budget and requirements really. This doens't necessarily have to cost much.
One of the most important factors though, would be educating the toddler, learning him that scorpions is totally off hands and to be respected!
I hope this helps a bit.