We arrive in Piraeus from Milos late on a Wednesday night in June. We don't fly out until the next afternoon and so we want to stay in Piraeus and visit the Maritime Museum the next day. Any suggestions on hotels in Piraeus for two adults and a preteen?

Hello friend,
to me Piraeus isn't the ideal place for a tourist to stay at, except if it's for a night as you said. And yes i am saying this, although i am Greek, i don't fancy Piraeus as a city.
Most hotels there are lower class and look somehow weird lets say coz the whole structure of the area is a little old and not so well maintained.
However i found one of Best Western chain (hope the looks don't scare you, this is how Piraeus buildings look like!sooo beautiful, huh?), that can't be bad anyways and it is 7 kms from the Maritime museum.
Try to google some more. Good luck and wish you a great holiday! Milos has awesome beaches!

http://book.bestwestern.com/bestwestern/productInfo.do

I forgot! Check the rest of the pictures of the hotel's interior, inside it looks much better!

http://www.mistral.gr/en/index.htm

Thanks for the feedback. I did look at the Park and the Mistral. In the end, I booked us into the Piraeus Theoxenia Hotel. Based on the website, it looks pretty nice, 5*, wifi, etc. I'll post a report on the hotel when we return in July.