Koznyshev

Congratulations on the acceptances! In response to your question, I think it's fine if you just let them know you appreciate the acceptance and leave it at that. That way you don't explicitly commit to anything. But even if you do I don't think it'll be that much of a problem, as they know the kind of stuff students do when applying (e.g., it's always more than one place and then it's weighing various options before finally committing to one place). Hope that helps!