Bad idea for anyone to be going out there now, especially for a horse race – the Iranians could easily change tact on what they class as a worthy target and with the Americans/English/French et al all taking horses out there to arguably Dubai’s biggest sporting event it becomes a very tempting target.
If it really goes pear shaped and air travel is shut down in the area then they could be stuck out there for who knows how long plus you are also dealing with natural flight animals that can easily be spooked by unusual noises let alone bombs and/or missiles exploding, which would scare the living daylights out of them and cause them to most likely injure themselves and/or those looking after them.
The risk/reward is so not worth it and you already have other sporting events in the region being cancelled due to safety concerns.