If you can work remotely, and if the kids are willing, I think that moving to a Spanish speaking country and putting them in the local school there would give you all a tremendous experience, plus they’d become fluent in Spanish. You’ll have to, of course, do a lot of research to find a setting where the local school options are appropriate and good. You could then decide whether to stay and let them finish high school there, or move back to the US and put them in 11th grade of high school in the US (I’d recommend not going back to the stressful, hypercompetitive private school, but instead choose to live where there’s a good public high school), and let them finish there, and do the normal college app process from there.
Yes, a Spanish-speaking country can be a good choice. When our kids were in grade school, we decided to take a “family sabbatical” and spent about half a school year in a small town in Costa Rica. We enrolled the kids in the local parochial school which was less than $100/mo in tuition. We chose the parochial over the public because the public had a lot more red tape to enroll, while the parochial required nothing other than the tuition. It was tiny; their classes had maybe 10 students each. It was not a “quality school” or anything like that, but that wasn’t the point; the point was having fun and improving their Spanish (full immersion-- nobody spoke more than a few words of English!) Our kids did speak some Spanish before going, but I have an acquaintance who enrolled his 7th and 9th graders in a Costa Rican parochial school for an entire year, even though his kids spoke almost none. Told the school not to even give his kids grades. His kids made a lot of friends despite the initial language barrier because they are outgoing and sporty (joined the school sports teams) and by the end of the year were conversing comfortable (although not perfectly) in Spanish. During this year he did tutor them in math so they wouldn’t fall behind, but otherwise just let them enjoy life. When they got back to the US, he just re-enrolled them in school, and said they had been home schooled. They were prepared to repeat the grade they had done in Costa Rica,but decided not to.