Democracy has proven to help us achieve great stuff as a society. So we can use a simplified version of it for the selection of which ideas should be pursued and which should not. We can use the dotmocracy technic:

At the end of an idea generation session, and once the ideas are sorted into categories, and the same ideas are stacked, give 5 stickers to each person.

People can then vote with their five stickers, they can put them all on the same idea, or they can split them between different favorite ideas.

Obviously you  can change the number of stickers, but as a rule of thumb, five stickers is the maximum I usually give to people. 

At the end of a dot voting phase I usually re-arrange all ideas from the one that has the most votes to the  one that has the least votes. The ideas with no votes stay where they were. This allows me to highlight the top 10 ideas that were created.