It's a little complicated, like a lot of things at O-A.
Has your kids' Spanish teacher told you they are ready for O-A type immersion model? Are your kids really excited about Spanish classes? Are they already secure in English reading and math? Do you and your kids have friends currently in Oyster? Are you planning on learning Spanish as well? Is your current IB school a mess? Would you be OK with teachers who can't speak or write in English? Is it cheaper for you to live IB than where you are now? Would you be willing to stick it out through 8th grade? (Research says it takes 4 or more years to be bi-literate and bilingual.) Are both the Oyster and Adams buildings (mile apart) convenient for you? Do you have a high tolerance for administrative miscommunication? Are you OK with being asked for money and/or time every couple of weeks?
The more yes answers, the more a move might make sense for you.
There are quite a few hard to quantify positives to O-A, like friendly and supportive families, fun events, respect for diversity, and some pretty amazing educators. For us, for now, the positives outweigh the challenges.
But we're always keeping our eyes open for other options. No school is perfect for all children.