"Would trail runners hold up on the 5 day trip alright?"
I through-hiked the PCT in trail runners last year, including Whitney/JMT portion in early June. 5 pairs got me 2600+ miles, using a shoe that's regarded as poor for durability (Golite Sundragon II's) so one pair of trail runners will surely last you 5 days (!).
In fact, trail runners or similar shoes have become the most common choice for long distance backpackers, no worries on that score. If you're still uncertain, bring a little extra duct tape.