Apparently I misinterpreted this rule:
Once you're finished with that house, click on "Manage Households" and choose another house.
I interpreted this to mean that you had to work one household at a time, and then move on to the next (as opposed to staying in one house and moving in single sims). That led me to a somewhat different strategy - I thought that minimizing the number of households was important. The most singles I found in one household was 4 (Calientes, Roomies, Partihaus) so I targeted those 3 along with Spencer-Kim-Lewis with 2 singles.
I planned to use Club extensively - to get sims to come where I wanted them to be; to improve the likelihood of romantic gestures succeeding; to keep Satisfaction high and eliminate the need to eat, sleep and run to the bathroom; and to get the whole group into a flirty emotion. The other key part of my strategy was to get all the targeted partners of each household identified before switching to that household so they were already in the club - this was to minimize the amount of time between the last date in one household and the first date in the next household.
I started with the Spencer-Kim-Lewis household, took them all to meet Geeta Rasoya, added her to the club and went to the park. I usually find Jacques Villareal sleeping on a park bench, so I planned to have Vivien go after him. If he wasn’t there, she could set her sights on a gardener, who would likely be an elder, but, if not an elder, well, bonus for Vivien.
Jacques was there, so Vivien chatted him up and then went romantic while Dennis chatted up Geeta. Eric and Alice chatted and flirted with each other to run up club points and also kept an eye out for anyone from the other targeted households to come by. Eric was the leader of the club Cupid's Cuties, so he needed to find a member of one of the other households to develop a friendship with - someone who would later be able to convince him to step down as leader. He also kept an eye out for potential spouses for the upcoming household. I planned to move to the Calientes second, as I thought there was a good chance of one of them showing up at the park for Eric to meet.
As soon as Dennis got a romantic relationship going with Geeta, he asked her on a date. He proposed during the date and they eloped as soon as the date was over. As soon as that date was done, Vivien asked Jacques on a date, proposed during the date and eloped as soon as it was over. By the time both dates were done, Eric had introduced himself to Cristopher Cruz, the adult gardener and added him to Cupid’s Cuties (partner for Katrina). Geeta had invited her son Raj to Hang out at Current Lot, and Eric met and also added him to the group for Nina. Salim Banali happened to be at the park, so Eric targeted him for Dina. Nina Caliente showed up, so Eric met her, added her to the group, and raised that friendship bar enough that when I switched households, Nina would be able to easily convince him to step down. Just as Vivien and Jacques were eloping, Annette Rocha showed up at the park. Eric checked her marital status and then added her to the group for Don. At this point, the group was Eric, Nina, Cristopher, Raj, Salim, and Annette, and I had targeted a partner for each member of the Caliente household.
At that point I switched households and Nina convinced Eric to give up the club leadership. She booted him out of the club, added Katrina, Dina and Don, and started a gathering. Everyone chatted and flirted, and Don was the first to ask for a date. As soon as the date ended, he and Annette eloped while Katrina and Cristopher started their date. And then Nina and Raj, then Dina and Salim. Most of the dates were at the park so the married sims could watch out for members of the next household and potential partners for them. I planned on going to the Roomies third, but Paolo Rocca jogged by, so Nina took the opportunity to meet him and chat him up so that they'd be good enough friends for him to eventually take over the club. Paolo started chatting with Maria East, so Nina checked her out and found that she was single. She added her to the club for Paolo. Nina also met and added Dandre Benjamin and Daichi Isikawa for Eve and Jada. But when the Caliente household dates were done, she didn't have a partner for Marcus.
I switched households, Paolo took over the club and went to meet Summer Holiday. He brought her back to the Partihaus, and started a gathering, which brought Maria, Dandre and Benjamin all to the Partihaus. The four couples chatted and romanced. Paolo already had some relationship with Maria, so that was the first date, which was at the Partihaus (to provide opportunity for woohoo). Paolo and Maria were married when Candy Behr came by, so Paolo introduced himself and removed Maria from the club and added Candy (he thought she was perfect for J. Huntington III). Marcus and Summer had the second date, and then Summer invited Mitchell Kalani over to meet Paolo and to be the next leader of Cupid's Cuties. She invited Liberty Lee over to be Mitchell Kalani's partner. Dandre invited his brother Ramiro over to be Zoe's partner, and Paolo added Liberty, Zoe, Mitchell and Ramiro to the club, ousting the married couples. Then Paolo went to Ulrike Faust's house, met her, added her to the club, and brought her back to the Partihaus for Gavin Richards.
I switched households, Mitchell took over Cupid's Cuties, and started a gathering to bring everyone together. Chat-Chat, Flirt-Flirt, Date-Date, woohoo, propose, and then elope when the date ended.
Congratulations to everyone who finished this, and especially to Minnie Mouse and LenaLJ for coming out on top!