Total nonsense, I'm afraid, and a perfect example of why translation websites should never be used!
Avoir un voyage fantastique means "to have a fantastic voyage" i.e. the infinitive, not the imperative. And saying "je vous aime" to a family member, especially a 12-year old one is just bizarre!
Ont is the third person plural of the very "to have" and means (they) have.
Me ramener quelque chose, again, is the infinitive, not the imperative.
Vous aimer means "to love you" when addressing more than one person or a person you don't know well - even more bizarre!
So, the French already have an expression for "have a good journey" - "Bon voyage". We even use it in English.
If you want to express the hope that someone has a "fantastic" journey, you'd need to say something like "Je te souhaite un voyage merveilleux!" Remember that "fantastique" in French doesn't convey all the meanings of "fantastic" in English.
To say "Bring me back something pretty" you'd say "Remmène-moi quelque chose de joli."
And, finally, to say "I love you" to just one family member, you use the phrase that most people know: "Je t'aime."