In my opinion, investing money that isn't mine into something too speculative is a huge no-no. Why not just use your own money instead? That way, you don't receive any crap if ever the investment goes bad. They already aren't convinced in the first place, so why force them?
Imagine you're at a casino with a friend. Your friend is hesitant to gamble, but you convince them to put some money down on a roulette bet. The bet loses, and your friend is angry at you for convincing them to gamble.
Investing other people's money in speculative investments is like convincing your friend to gamble at the casino. It's risky, unethical, and a recipe for disaster.