Does your colleague have experience driving or are they also new to this?
Look, it's exciting to have a freshly obtained license, but starting with a long coastal trip has risks. It's not impossible, but you need to be realistic: highway driving is very different from practice sections. I'd recommend starting with shorter trips first, maybe 1-2 hours, so you can get comfortable with speed, lane changes, and traffic flow. If you still want to try it this weekend, only do it if your colleague is a good driver and can take turns, and if you plan to drive during the day (no early mornings).
Basic precautions: check the car thoroughly beforehand (brakes, tires, fluids), don't drive if you're tired and don't drive more than 2 hours straight without stopping. Keep distance from other cars, don't speed or do unnecessary overtaking, and forget about your phone completely. If you feel nervous at any point, don't be embarrassed to pull over, get out and take a breath. Also don't eat anything complicated while driving.
Honestly, it'd be more sensible to practice on local routes first and do that coastal trip in a month or two. But if you go for it, don't drive alone and be super careful 🚗