What's the Name of That Book??? discussion

This is a series of about 10 children's books. I read them somewhere between 2007 and 2011 in French but I'm assuming it was a translation. They were about 200 pages each. There were three main characters, two boys and a girl, all teenagers. Here's what I remember from the plot:

- These kids can travel through time and space. Each book is set somewhere different. The main guy is from the present (2000s US) while the girl is from the middle ages.
- The first book starts off in a big city with the main guy pickpocketing someone and awakening to some kind of powers. The three kids are assembled and taken to some other planet/world where they're told about their powers and what they have to do.
- Either in the first or second book, as the kids get to know each other they have to learn to get along with a clan of magical creatures (centaurs perhaps?)
- Also at the beginning of the series, the kids take over a castle and meet a wizard lady who helps them throughout the series. It's revealed at the end that she's the main guy's mom.
- The girl gets kidnapped at some point.
- One of the books takes place in the girl's hometown where they meet someone who was branded as a witch because she knows how to use medicinal plants. The girl is noble/royalty and I think they all meet her parents.
- One of the books takes place on a planet where there's illusory magic. The three kids get separated and each get lost in a different maze. As they rejoin and escape, they realize the planet is actually a giant sleeping creature floating through space. There's something with sleeping gas either in that book or the next.
- One of the later books involves pirate ships and dangerous mines (possibly near a volcano). Someone falls in water infested with dangerous creatures.
- In the last book, it's revealed that one of the main antagonist was actually the main guy's dad. Some kind of difficult decision has to be made, and gems have something to do with it.
- By the end of the series, the main guy and the girl get together as a couple.

Any guess is appreciated!

Based on the description provided, the series you are referring to sounds like "The TimeRiders" by Alex Scarrow. This series consists of time-travel adventures with three teenage protagonists, exploring different time periods and facing various challenges, similar to the plot points you mentioned.

That's not it unfortunately, none of the plot points seem to match. The series I'm thinking of was more fantasy than sci-fi and had nothing to do with real world historical events.
I'll add that the whole series was already out when I read it, I said 2007 to 2011 just to be sure but it's most likely 2007 to 2009 in reality, 2011 is a hard limit.

My sister somehow found it with her crazy googling skills, it's the Diadem series! (Book of Names for the link)

Glad you found your book series, LesLoue. Thanks for the update.

Book of Names (book 1) of the Diadem Worlds of Magic series by John Peel