Leaving Laos

I'm on my Spring Festival jaunt. I'm currently in Hanoi, moving on to HCMC tonight, Cambodia on the 8th, Thailand on about the 11th and then into Laos on about the 15th. The idea is to cross the Thai/Laos border at Chang Rai and head straight for Luang Prabang. The question is where to from there? As I see it, I have 2 or 3 options. 1) Cross the Chinese border somewhere neas Xishuangbanna and spend a bit of time there but I don't know if this is really possible. 2) Get the bus from Luang Prabang to Kunming and, from there, head to Lijiang for a day or 2. 3) Re-enter Vietnam at Dien Bien Phu. Head on to Sapa, Lao Cai and go back into China Hekou or return to Hanoi and get the train to Nanning but, to do this, I will need another Vietnamese visa (NZ passport). Everyone in Hanoi is telling me that visas are easy to get on the Laos/Vietnam border but I have my doubts (Never actually having got a Vietnamese visa at any border before) I'm due back in Beijing on the 22nd. What does TT think?

No, you cant get a Vietnamese visa on any land crossing. Unless they're actually talking about the Laos visa.
Theres only one border crossing between Laos and China and its at Borten/ Mohan.
+but I don't know if this is really possible+ Whats there not to be possible about?

Possible as in where is this sole China/Laos border crossing in relation to Xishuangbanna? Is it possible to decamp from the bus as one crosses the border to visit/get there or will the powers that be demand that one goes all the way to Kunming (In which case, going back south wouldn't really be worth the time and effort)? It was the Vietnamese visa. At least 2 travel agents swore themselves blind that it was perfectly possible to obtain a Vietnamese visa at the Laos/Vietnam border crossing (“Easy”, they said. I will probably have time to sort out another visa in Bangkok, if it come to it anyway) but it's looking like the bus to Kunming then heading back up might be the best idea.

Oh, okay. We've done it twice but headed from the border to Mengla then on and up towards Jinghong and Dali.
If I remember correct, arent you also on a NZ passport? If so, then no, you cant get a visa at a land crossing into Vietnam. Of this I am 100% sure.

The direct Luang Prabang bus isn't the only option on the route from Laos into China: You can catch a local bus from Luang Prabang to Oudomsai (Laos), and then a bus (there's at least one a day, maybe two or three) from Oudomsai across the border to Mengla (China). The main base for travelers to Xishuangbanna is Jinghong, which is about 2 hours or so by bus from Mengla.

An alternative possibility would be to travel from Luang Prabang to Luang Namtha (a pleasant, tourist-friendly town in the north of Laos), spend a couple of nights in Luang Namtha, and then catch the daily direct bus from Luang Namtha to Jinghong (about 8 hours).

Unless you're really into long bus rides, stay away from the Luang Prabang-Kunming bus. There are plenty of local bus options along the route, meaning the long distance bus is only convenient if you're in a rush to get to Kunming.

From the border in Chiang Rai province, there are two options for getting to Luang Prabang: by far the most pleasant is the boat, but this will take you 2 days. Alternatively it's something like 15+ hours by bus. The bus route will take you only an hour away from the main Chinese border, so heading back up to China afterwards will involve a fair amount of backtracking.