Just a thought - Do children pay lower entry fees than adults anyway? Are there special prices for family tickets? Would you let any child go round a theme park on their own? However, if the theme park does offer free entry to disabled children, then worth asking them what evidence they want to see - and perhaps carry a translation into local language with the letter. It's very unlikely that you would have a "Blue Badge", as it's associated with restricted mobility, basically equivalent to Higher Rate Mobility (only available to children over 3 years), while children over 5 years are sometimes awarded Lower Rate Mobility, if they need to be accompanied outdoors. "Blue Badge" is recognised throughout European Union as an indicator of physical difficulty in walking/
Generally, concessions for disabled people are for those who couldn't go without a carer - generally adults, who could otherwise go alone.
