The engineered hardwood floors were delivered 5 days ago for a flooring install tomorrow morning. In the meantime a cold front in Houston has dropped temps from upper 70's to the 30's since the wood was delivered. More importantly indoor humidity has dropped from +/-50% to 35% right now and dropping (with the heater off). The Bostik Glue bucket says slab temp should be 50 degrees or higher which I am assuming is fine since the indoor temp right now is about 60. Question is should I proceed with the install tomorrow or ask them to delay it? Temps/ indoor humidity will be dropping all night as we have a hard freeze expected in the morning. Am I overthinking this???

Yes. Overthinking

If the material has been opened then it may have dried out a bit with the introduction of the dry heat to combat the cold. Just leave an extra 1/8th for expansion around the perimeter if thats the case.

If the material is still in boxes, it should be fine to install. There may be some gapping post-install as the dry heat shrinks the material but it will recover in the spring.