Unfortunately it doesn't seem like there are any Spanish schools or schools that teach the Spanish curriculum.
This leaves you with schools that offer a Spanish class, where the rest of the curriculum is in English. You could consider homeschooling, but this will be very time intensive or you'd have to hire a tutor. It's also worth noting that, while the Dubai government doesn't explicitly prevent homeschooling for expats, it also doesn't recognise it in any official capacity.
There is also the possibility of doing correspondence courses through a Spanish institution such as, for example, EIDE.
Unfortunately it doesn't seem like there are any Spanish schools or schools that teach the Spanish curriculum.
This leaves you with schools that offer a Spanish class, where the rest of the curriculum is in English. You could consider homeschooling, but this will be very time intensive or you'd have to hire a tutor. It's also worth noting that, while the Dubai government doesn't explicitly prevent homeschooling for expats, it also doesn't recognise it in any official capacity.
There is also the possibility of doing correspondence courses through a Spanish institution such as, for example, EIDE.
To get a better sense of the system there, have a look at Education and Schools in Dubai.
Good luck,
Xavier