Will be traveling this summer with my husband and two teenagers to Istanbul (as out base) and Milan. We have a few days to do a beach holiday and thought of Bodrum as a quick trip from Ist and have already booked at the stunning Mandarin Oriental. Friends are saying Mykonos is nicer and that we should consider that instead of Bodrum. We like nature, history mixed with beach bumming. Any thoughts?

Mykonos is more beach bumming. It is also a party scene and a top destination for homosexual travelers, if either of those facts matters.

There are dozens of Greek islands much nearer the Turkish coastline than Mykonos, which would require flights via Athens or a long ferry ride or two from Samos. From Bodrum you could take a day trip to the Greek island of Kos.

I thought people wanting beaches in Turkey usually went to the south coast.

Don't worry: both places will be crowded in August, both will have tons of discoes and will be noisy in the center.
In August, it's much easier to find a taxi at Bodrum than at Mykonos.
Bodrum is much bigger than Mykonos, with much more road traffic, although there are some pedestrian zones (for example along the old harbour).
At Mykonos, it's easy to find nice (although rather crowded) sandy beaches relatively close to the center (frequent shuttle buses) whereas from Bodrum, you have to go farther away for that.

The Mandarin Oriental is more than 10 miles away from Bodrum, however and has it's own beach, even a bigger one than the Hilton, which is close by.

Thank you for your replies

I would not compare the two, as they are completely different...
Mykonos is a small island with great beaches and a great night life.... You don't have to be a club goer or gay to visit Mykonos, and i will say again in this forum, that one can have very calm holidays on Mykonos regardless of the party scene... ( i am visiting Mykonos 30 years now, a few times per year.)
From Mykonos you can visit Delos, one of the most important archaelogical sites of Greece.

I would not think however that Mykonos can be reached easily from Bodrum.... so i would recommend to stick with Heimdall's advice if you want to visit a greek island and choose Kos.