I would not rule out Priceline or Hotwire.

Hotwire has a bed choice option in some cases. In addition, if you are careful about trying to properly identify the hotel, and you put 2 adults and 2 children in the search box, you can likely figure out if it is a hotel that typically offers 2 queens.

For Priceline, it is often the case that you can get 2 rooms for the price of 1 booked in the ordinary way. With the right star and zone choices, you nearly eliminate the risk of just getting one double bed -- most often it will be a queen in all but lower-starred hotels and expensive cities like New York. (This applies to the USA, not elsewhere.)