I'm sure the techies will provide some good infor about the right wheels (All of mine are custom built but I can't give you details) but something for the group to comment on - 29 v 26 wheels when someone is large. 26 wheels are stronger due to smaller size. With 29wheels really need to consider something bomb proof. It's not that expensive to replace new/stronger spokes but you might want to consider buying new wheels - something built for downhill riding (which means they are stronger and heavier). You can get a decent wheelset for $300 ( a buddy of mine who weighs just this side of 300 bought Azonic Outlaws for $325). That is really less than new rims and spokes and having it relaced (I spend upwards to $1000 for a custom wheelset but it can be done for around $300 - 400).

Azonic does make a 29er

http://www.azonicusa.com/wheelsets.php

Double-wall, welded, design rim with a wide profile for extra strength and rigidity
32 spoke construction for added strength and pedaling efficiency

And again the reason I mention Azonic is they specialize in downhill wheels which because of use are just built stronger.