Hello, I also have three kids, two now at a London day and one still there. Dolphin has been a fantastic school for all three of them.
In answer to your first question, it's both academic and creative. The ethos is very much to celebrate each child's strengths, whether that's in maths, English, science, sport, drama, art, music, or all of the above. The focus on academics is core, and the school is small enough that all the staff know each child's abilities individually and can cater to them. The children are challenged but not pressured, if that makes sense.
But there's also the recognition that children need much more than just being pushed to pass exams, and that's what makes it such a special place. The sports provision is excellent, both competitive and nurturing, with all the children given opportunities to play and learn even if they're not naturally sporty (like my older two). Music fills the school, and there are frequent recitals and concerts to showcase the children's progress, even if they're just starting out with a new instrument, which is amazing for their confidence. My three have also really enjoyed the drama -- from Reception, all the kids get to perform on stage during assemblies, nativity plays and the end-of-year production. Again, so good for their confidence, especially for the more introverted ones like mine.
I think the word "religious" can, these days, have a negative connotation -- that's certainly how my husband uses it, anyway. As a staunch atheist who's had a very Catholic education, I wouldn't say Dolphin is religious in that negative sense. It has a Christian ethos, which I love because the kids learn respect, compassion, kindness and all those other important life values. There's none of that "non-believers will burn in hell" stuff I had when I was in school. Rather, my kids have taken away a good knowledge of the bible (very useful for art and cultural references), the ability to think critically about everyone's beliefs including their own, and, most importantly, tolerance and understanding.
The head, his senior team and the staff are brilliant and make the school a happy place that kids (and parents!) look forward every morning to going to. I do hope you choose to take a look around. Please message if you have any more questions.