Three days for both is possible but take late ferryboats or planes or it'll be difficult to leave early in the morning after a good party ;-)
Better go to Mykonos if your priority is nightlife.
I disagree, it's NOT possible if you plan to do anything other than unpack, go party, pack up and move on. With only 3 days, choose one island and give yourselves a chance to have some fun. If nightlife is your priority then I think Mykonos is the one for you.
I mean that it is possible theoretically but undesirable :-))
Of course you're right, I should have said the same thing......
I am guessing from a quick google that LDW is end of August? (outside of the US, phrases like 'labor day weekend' dont strike immediate recognition :-)
In which case, its still high season so you are being way more than optimistic to think you can book hotels, ferries flights to line up for one island, let alone 2. And sorry but 2 islands in 3 days is just plain silly, you'll spend literally more time travelling than being anywhere.
If nightlife is the priority, the overhyped overcrowded overrated island of Mykonos is the one for sure.
If nightlife is a priority, I would definitely go with Mykonos. Do not be turned off by Joe's comments about Mykonos being overrated, overpriced, etc. I think if you know what to expect and know what you are going into, you can have a great time at any of the islands. I still have no clue why so many people have such negative comments about Mykonos. If it is not their cup of tea, then just say so but giving such negative impressions of what can be a great island if you know what you expect when you go there is not very helpful on this site. I agree with the comments that 3 days is not enough time to do both islands as you will spend a significant amount of time actually travelling between the islands. IF you want nightlife, then head to Mykonos (I will be there over Labor Day Weekend in the US). If you want relaxation, quiet and a beautiful location, then I would go with Santorini. I usually do at least 3-4 days at each location. Any less, then I do not think it is worth it.
25 Euros to reserve a couple of loungers and a parasol? If thats not overpriced ......
Good choice. Perhaps we will run into you while there. It does not cost 25E to get a lounge chair and an umbrella but at only one place at the island that I am aware of. If you choose to go to Nammos and spend that then you that is your choice. It is an experience, but you pay for it. The other beaches on the island charge about half of that for the use of the lounge chair and umbrella. Just plan ahead and you will have a great time.
"The other beaches on the island charge about half of that for the use of the lounge chair and umbrella."
Ahhhh, only double (or more ) what it is elsewhere on nearby islands. Not overpriced at all then :-)