As Norm said above, its about 90 minutes from Dubai to Abu Dhabi. Traffic is rarely an issue in my experience so no need to account for that really. We spent about 2-3 hours at the mosque. In that time we did the free English tour, plus a seperate stroll around the mosque on our own, and then a quick stop for a cold drink at the coffee shop there. So I think you will easily make it there and back in time for your flight. The Mosque is seriously impressive, you will not be disappointed.

It’s free for entrance. You need to bring your valid photo ID with you. If you are female, there is a dress code. Opening hours are 9:00-22:00 Saturday-Thursday and 16:30-22:00 on Fridays. But note that it’s different during Ramadan. 00am-14:00 Saturday-Thursday and the mosque is completely closed on Fridays. They also only offer tours at 10:00am on the days they are open. You can of course do your own. There are two options. If you plan to stay in Dubai, One is taking a bus from Main bus terminal in Dubai( Al Ghubaiba bus terminal) to Abu Dhabi bus station. But you might need to take another bus or taxi to the bus terminal in Dubai and to the Grand Mosque from main bus terminal Abu Dhabi. The taxi fare is considerably cheaper that the one in US. If you took one for 15-20min, the fare would be 30-40AED(8-11USD). And the bus fare to Abu Dhabi is 25AED(6.8USD).But it would take around more than 2hrs in total. My recommendation is another way, taking a taxi directly from your place in Dubai: it would cost 250-275AED(68-75USD). And you can get there around 70-90min if the traffic is okay. You can use meter taxi or you can negotiate it with taxi driver. You can also use Uber, by make sure you get a 50% discount coupon. It would be as expensive as taxi fare if you you use it. Otherwise it would be around double price. Uber in Dubai, the driver is offered a LEXUS CAR by Uber contractor company. So you can consider it as nicer version of taxi. There are many taxi waiting outside the Grand Mosque. I would recommended you to stay one night in Abu Dhabi. On the first day go to Grand Mosque in the morning at earliest time. It would take 1-2hrs to go around. Then you can visit other spots in Abu such as Emirates palace (7star hotel) by taxi. On the second day I would use a whole day to go to Ferrari Park and Yas water park by a combined one day Pass. For Yas water park definitely better buy Fast Pass ticket if you wanna ride all the water slider instantly for all day. With a normal ticket you have to wait for 30min or more for each time. This is all to your question. Feel fee to ask me if you got anything. As I live in Dubai, I am willing to help your questions