Thank you everyone for the prompt feedback! I've made initial contact with a couple drivers from the other thread - I plan on going with one of them. As for flights, given the route, looks like no point in waiting so I'll take a look at travelzen & ctrip again and then pick the best option before applying for our visa tomorrow.
I did look at Yangshuo mountain resort - that one looked really nice as well! I'll definitely consider the river cruise you suggested as I have not made specific plans yet for our time in the Yangshuo area.

Thanks again!