This sounds like a fun premise–I love the Indiana-Jones-esque feel to it. 🙂 However, right now this query clocks in at 282 words, which on the long side, and it reads more like a synopsis than a query letter. There’s a lot of information in here that isn’t critical to helping us get a sense of the story (e.g. sentences like “Not wasting any time, his father quickly sets out to give a guided tour.”). Generally, a query reads more like the sort of blurb you’d find on the back cover or inside the dust jacket of a book—a teaser, if you will, to entice the agent to read more. And in the end, that’s really all you need to do: if you get the agent to request pages, your query has done its job. 🙂
So how do you write something that will snag an agent’s interest? Well, the four main points that any query should hit are as follows:
1. Who is the protagonist?
2. What does s/he want?
3. What is keeping him/her from getting what s/he wants?
4. What are the stakes (i.e. what will happen if s/he fails to get what s/he wants)?
So at this point, my advice is to go back to the drawing board and focus in on your protagonist and his problem, because that’s where your query truly begins. Also, since this is historical YA, you don’t need to work so hard to set the scene for us—any reader with a decent high school education is going to have a pretty good sense of what the global political scene was like back in 1941. Right now, your first two paragraphs contain a lot of fluff, and you can summarize all of that in a couple of quick brushstrokes (this isn’t a very good example, but just to give you a sense of what I mean):
“When fifteen-year-old Will Evans leaves his dull London boarding school to visit his father at the Museum of Antiquities in Cairo, Egypt, he’s more nervous than excited.”
Finally, if you haven’t already done so, you may find it useful to go read the blog of the Query Shark (http://queryshark.blogspot.com/) and see the kinds of things agents do and do not want to see in query letters.
Hope that helps, and best of luck with this!