Prayers finish at 1:00pm not start so think about an earlier time
Imagine a Rak member coming to Dubai (ibn Batuta) and then travelling to Yas marina, the poor member would have drained half his energy just travelling one way (karting takes a lot of energy)and he has to go back too. So keep a neutral Venue either sharjah or dubai and trust me nothing to offer other then the Yas marina IMHO. Sharjah, Rak, Or Fujairah has lot more driving roads then Dubai or AUH.
In these months enjoy the weather go out doors, indoors things can be done on warmer days.
My Suggestions should you accept.
A. Try Musandam, Beautiful road , beach and scenery
B. Try Kalba, Same as above
C. Try a Desert BBQ during the day or night
etc
Just my pennies!