If you need a different antenna pattern for 5GHz as for 2.4GHz, this is not possible with the AP-134. The AP-124 could be tweaked to do that, but it came with severe restrictions and was never a recommended scenario.
You will need to pick the right set of dual band antennas for the AP-134, which is driven by the gain and coverage pattern you need. AP-ANT-19 (you'll need three) is certainly an option, but I can't tell whether that would be the best solution for your needs. The AP-130 series ordering guide (on Aruba website) lists your antenna options, and you could check the antenna datasheets to pick the right one for your deployment.
The AP-134 with AOS software supports mesh links, but this is really only suitable for no more than 2 mesh "hops". The main focus of these products is access. If you're deploying a larger mesh network, the Airmesh products may be a better option.