Grade school magical adventure book; secret door to ancient egypt

The book I am looking for is the first one in a series of grade school level magical adventure book, which I probably read sometime between 2008 and 2012. The first book is about some kids who are living in a new house and begin to discover strange things about it. They find a long staircase leading down to the sea, near which there is a cave which holds some old artifacts that give them clues that lead them to other things. Eventually, around the end of the book, I believe they find a door in the house that takes them to ancient Egypt. I hope that's enough and that somebody can find this book as it has been bothering me for months.

The Door to Time by Pierdomenico Baccalario?

Wow that's it, thank you so much. Looking at it now, I'm sure that it was the right book but am absolutely amazed that you were able to find it based on my description as I now realize that it wasn't very close to the actual thing.