If you disable everything I stated, there should not be a possibility of a wipe or reflash without first restoring the data you removed. Although I am sure a carrier reflash will restore the data.
They have the IMEI and serial number and all pertinent data for the phone, the casual toying with it should cause no harm, especially with children too young to know how to do such things, you should be safe.
But as history has taught us, there are always ways a fool can make foolproof things work.
Enough monkeys and typewriters can type out the complete War and Peace novel, they simply require the time to do so.
This is why you need to write down every piece of altered data before you reboot, otherwise, you may have a difficult time guessing what goes where.
As noted previously, *#*#4636#*#* only disables the radios TEMPORARILY, and restores the phone on reboot.
If you really wanted to remove any chance of 'accidental' 911 dialing by your kids, you can open the root browser and alter the build.prop files to remove the CDMA settings the phone stored, and also wipe out the ro.build files.
If you go deep enough in the file structure, you can turn the phone into a brick if you desire, just by wiping out the radio data, except anything that points to the WiFi configuration, as you will need this.