, ditch the plenum and go with a DSB
temp only matters if it goes to extreemes. If you use a cooler or rubbermaid container stuffed with newspapers or other insulation you should be ok. you don't have to keep the LR
submerged, but the wetter the better. perhaps once or twice during your drive pull over and splash some water over the rocks. you don't "have" to do it, but i think it would help to minimize any die-off (which is what will cause a new cycle when you set your tank back up)
water should be fine in a container for a few weeks as long as you can keep contaminants out of it (just use a lid) and a bubbler, again, not necessary, but couldn't hurt.