Visiting the Europe office

So I'm finally taking my post-grad vacation overseas, and I would like to visit a coworker who is relocating to our London headquarters office when I go. Its a well deserved trip, and should be taking place right before my "expected" promotion (or at the very least, a raise.) My manager/director thinks that when I'm there I should stop by the main office and have drinks with his counterpart, the current London director of our sister department. He also thinks I should have drinks with the former director of a third branch of our department, who is also relocating to that office. While I'm 100% ready to mix after hours with co-workers at home, or even on a work trip, I'm conflicted about whether or not to spend part of my vacation networking, which is like my least favorite thing to do. Should I make plans to meet everyone one night, and extend my trip by a day? Or should I continue with my plan of only seeing my friend, and continuing my trip without drawing attention to myself?