Greetings.

Must be a clever child to be 5yrs old and already knows how to read/write & use IM programs.

Maybe implement a filter list on he's/her's user profile so that the child can only visit website's within an approved list.

This can be done via most routers in the settings area.

Or even the parent's/yourself could always just monitor them while they are using the IM programs.

most IM programs have an option to auto-save all chat logs into the relevant application folder. Just enable that also....