This is a crappy question, which will likely be closed as opinion-based, so I will respond without restraint, just because this is all intensely interesting to me, but actually backing up my claims would take hours and hours.
Your two motivating paragraphs are both baseless.
Failed relationships do not lead to murder, but intimacy is a way in which the troubled structure their feelings. One way of looking this is that most murder in the name of love has roots in Borderline Personality traits which express themselves against those we love. But people with Borderline threads in their personality do not suddenly get sane outside of relationships, they just get more bizarre to more different people, when they do not have a single person on whom to lay all of their weirdness. They undertake high-risk nonsense and someone is still just as likely to end up dead, but who that is, becomes less predictable. (By that theory the level to which we ignore Borderline threads in men, perceiving them as Antisocial instead, explains a lot of the difference in rates of spousal murder between the genders.) [Pardon the odd capitalization, it emphasizes that these are words with technical meaning largely unrelated to any normal usage, to normal people 'borderline' involves some kind of border, which is absent from its diagnostic use, and 'antisocial' means misanthropic, not prone to threats and abuse]
Most things with high correlations with death are not outlawed. The drug most likely to lead to murder or is generally legal. We do not outlaw sports that kill people. We consider choosing an outright deadly occupation a personal choice, and the number one employer in the occupations most likely to get you killed are government bodies. Most things with high correlations with imprisonment are outlawed. But that is because doing something that is outlawed is how you get imprisoned.
I do think that it is unethical to pump up romance unnecessarily. Especially since this is generally done for others' personal gain. Romance is an industry in this culture, and it preys upon a part of the population with a specific weakness that makes them rather impractical to begin with, the young adult. (One way of looking at Borderline structure to begin with is that it is unfortunately extended adolescence.)
From a male feminist point of view, the male side of this problem is particularly bizarre. The fact that men are romanticized through display of potential protective traits, and that we have largely displaced protection from individual action onto the state makes for a situation where men are encouraged to endanger themselves and others to prove they are evil enough to be useful. This warps our notions of 'evil', 'useful' and 'danger' so completely that our means of defending ourselves is highly compromised.
Since jealousy is natural, and so is transition between lovers as our psychological needs evolve, we have solidified obligations in a way that does not allow for our longer lifespans and in the process we have extended childhood to a degree that creates fragility. A family, once attained, is overly permanent. It survives its own death, in the form of financial bonds that maintain a childhood that has been artificially lengthened by at least one third. So there are barriers to forming families 'prematurely' by which we mean "at the exact time in life that led to the most stable families throughout history."
A more realistic view of this interferes with the cultural distortion of romance, and cannot get traction. Whatever you teach your children, they will likely adopt the cultural standards and not yours.
Monogamy is also shaped differently for the two genders in a way that is destructive to psychological order. We have a prejudice that female traits are 'better', because we have allowed women to be the primary shapers of children's morality. This impairs men morally by implying that morality is something inculcated by the 'other', rather than a natural internal process. In particular, it makes us adopt standards like monogamy, but also to defensively amplify them. Even women are nowhere near as naturally monogamous as the structures of most cultures presume. The result is a ludicrous amplification of jealousy in men, who are taught that they are giving up their natural feelings for something better, and then feel betrayed when this investment does not pay off.
The modern backlash against all of this is in scale with its stupidity, but it is strangely directed, because it is continually shaped economically. We are being herded into a cultural center where sex goes back and forth between being free and easy and being rigid and alienating, because there is money to be made on both ends, but not at any sane point in the middle. We have a cultural milieu for 'hooking up' and another one for 'being a family' but we do not have places where money circulation can be increased by leveraging those who are not on one of those tracks.
For example, divorce is very odd: there is not a slow and natural problem-solving process for dissolving a relationship, with adequate support of those involved. Instead there is an abrupt cliff where long-term decisions are made in the heat of intense disappointment, and frozen in documents that are awkward to renegotiate. Money is extracted from the family structure at this point and at the points of renegotiation, but these are points where it should be injected, to even out the transition. And even though divorcees are a major component of society, they barely fit in until they return to one of the approved (profitable) statuses.
So no, don't indoctrinate your children into an endless 'hooking up' culture by telling them monogamy is a lie. Lead them to understand that stabilty is rare in so complex a society, and how to value it, without becoming obsessively attached. And primarily cultivate values of authenticity so that they know when they are being manipulated. Defense against having your values overpowered by larger institutions is going to be a major component of life as rhetoric, through the volume of media exposure, again becomes a science.