Legalize weed, don't market it towards children, let adults do what they want if they're not harming themselves. Substance abuse problems (which are entirely different from the issues surrounding smoking, which wasn't "cool" but just "the thing that literally everyone does" prior to advertising) are mental health issues more so than access to a substance issue. People become alcoholics because they're genetically inclined towards the it or because they are trying to escape something about their circumstances (or frequently both).
TL;dr- Plenty of people already smoke weed, and nobody advocating legalization is advocating for people to be allowed to drive stoned or let children buy pot.
"Will Kids think it's cool" isn't really a good argument in favor of prohibition. If anything, so far the (small amount) of data seems to show that legalization doesn't really impact things too much in regards to kids smoking in states its been legalized in. The teen usage is about the same, but it's still a super new thing so who knows how that plays out long term.
I admit I did not studied this topics since I am not interested just I am very disgusted on the tabacoo industry advertising and lobby and I would like to not repeat the history. I am not for prohibition, make it legal but don't have that a dozens of people get rich on this and society pays for the consequences.