I can hardly believe you're considering this, such a bad impression, and if I may say so, not a very good attitude.
Your course should be your priority, and your department will expect that it is. Like some people have said, you could get away with non-registered lectures, but not seminars/tutorials/labs or anything like that which you have!
And even if you did get away with it, it would have a serious impact on the rest of your semester.
I have missed large amounts of session in the last semester I did (up to 45% in one module) due to illness, but my absences were very rarely seminars/tutorial, and were spread throughout the semester, so catch-up work was much more manageable. I wouldn't recommend it though, especially if you're in first year because learning from lectures does require more than just copying off whatever's on the slides that get put online.
One of my lecturers knew about my absences and the reason behind it, and actually commented that she was pleased with my good standard of work *considering*. But if you're going off for a holiday...they will not be impressed, even if you still somehow managed a first.