Too similar?

As long as it's a unique plot I think you'll be fine. People may say things lie that anyway...it happens to the best of authors as well. Ignore it( I know that's harder than it sounds, but it's true). If it's different and the only similar factors are the children entering the magical world, and trying to save it...and becoming warriors along the way...honestly, there are tons more books like that than just Narnia. People have been doing it forever. All in all, I sounds a-okay to me. Good Luck..:)