UK travel 14+ days before start date possible?

Hello all,

I am thinking of applying for Tier 2 visa soon, and the job start date specified in CoS is Jan. 3rd 2018. As far as I know, all applicants are allowed to enter the UK up to 14 days before the start date that means it's not permitted to enter the UK before then.

Actually, I am planning to visit my family living in the UK around 12th Dec. that is before the allowable date, so that I am really afraid of it. I am considering that I will enter the UK as a tourist at that time without a visa because visa-free travel is possible for the passport holders of my country up to 6 months. After then, if necessary, I will travel to the other Europe countries with my families and come back to the UK within the 14 day period before the start date using a Tier 2 visa issued. Does it make sense? Otherwise, isn't there a better way? Please give me some advice. Thank you so much.