Hi,
If that site has two languages, you should create separate page for each language, it's how it works in Joomla:
- Spanish - Page 01
- English - Page 02
then in each page - you can use native languages in all addons. This seems the most sensible & popular solution used by 90% webmasters (the others use google translator module).
OR you have to hire php developer from your city/country that can customize you current addons code. For somebody smart it's quick job, so it shouldn't expensive, and your clients pays for extras, right.