Season 6 activities follow : Bran Stark
As far as I know, which I could be wrong, when Bran and Co. were under the hill, chillin with the trees, Bran was in a vision and got touched, thus breaking the enchantment keeping the White Walkers out from under the hill and thus they were able to get in / attack the children.
Upon his recent activities, he'll most likely be heading to Castle Black with the aid of Benjin and then he'll be breaking the enchantment on the wall, allowing the White Walkers access to and beyond The Wall.
Dragonglass / Tyrion
If I recall, Dragonstone is bountiful with dragonglass, and Tyrion may suggest they stop there to get some before heading to King's Landing, as he's been to the wall, he drinks and he knows things, so he may be more keen to the fact that the White Walkers are coming and are a threat.
Dragons
[They're still not really reliable, and if they are, Danny needs to get her shit together and start using them rather than going on sky drives for no reason other than having thousands of people wonder if it's Superman. She's only really used them to attack people like, twice, even when everyone was being attacked in the arena during the slave olympics, she just rode away and left everyone for dead. Either way, they would be very effective against the White Walkers, however, I feel like she's just worried about the throne and not thinking far enough in advance.