3.5 year old help 😳

Heya all. So we are on a vacation with family. My kids are 3.5 (4 in August) and 1. My eldest son is not sleeping at all. He typically takes a 2 hour nap every day at home and sleeps all night from 9-7am. Since we have been on our trip he is not sleeping at all. Skipped his naps and his not sleeping at night either. Last night he was awake until 2am and woke up around 6am. His energy level is insane because he is so exhausted. He’s bouncing off the walls and fighting with everyone. I don’t know what to do? I tried so hard to make him sleep last night but he was just tossing and turning. I have tried to keep his schedule the EXACT same and make his sleeping environment the same, we brought our fan and white noise machine and he has his own pillow and blankets. I know only sleeping 4 hours a night is unhealthy for an ADULT, I can only imagine what it is doing to his little body. Please help? My mom thinks we should give him Benadryl?