I live here (Flagstaff) and lived there (Las Vegas).
Now in Flagstaff (north of Sedona, and on the way to the Grand Canyon).
As far as I know, the North Rim of the GC is closed (due to snow) until May. The south rim will be open, and not as nearly crowded as later in the year. You may even be able to drive your car into the park and along the rim. I would recommend coming in (or out) the south entrance, and leaving (entering) by the east entrance (to/from Cameron, Arizona).
If you have time and inclination, check out Antelope Canyon (near Page, Arizona - need a local Navajo guide - and a modest wide-angle lens). Also, the bridge and dam at Glen Canyon Dam/Lake Powell are worth a stop.
As noted by others, go for the some kind of National Park entry permit. You should consider Zion National Park and Bryce Canyon (may be snowed in) on your trip, in addition to the Grand Canyon. The Grand Canyon is one of those few places on earth that exceed expectations. My wife says the only other place she’s seen that beats expectations are the fjords of Norway (if that is relevant).
If you get to Sedona and are still headed north, consider the route 89 road from Sedona to Flagstaff - very scenic.
As somebody noted, in Las Vegas, Red Rock Canyon is worth the visit. And, north of Las Vegas (on your way to Zion/Bryce?), check out Valley of Fire state park. Include a scenic drive along the shore of Lake Mead. If you cross the border between Las Vegas and Arizona, stop for a walk along the bridge just below Hoover Canyon Dam (need your widest angle lens here).
Check out local bars and grills - way better than Starbucks . We have a favorite just a mile away where we eat every Sunday (9 miles north of Flagstaff). Not real cheap, but reasonable (on the way from Flagstaff to the Grand Canyon - let me know by PM and we might meet you for dinner!!)
“I'm also curious about visiting one of the aeroplane graveyards (I am a pilot)” Oh my god, you MUST visit the airplane museum in Tucson (
Pima Air & Space Museum). Be prepared to spend a LOT OF TIME. Not sure if foreigners are allowed, but also schedule a trip to the Davis Monthan Airbase “graveyard” - more Air Force planes in cold storage than you can possibly imagine!!!!! Our US tax payer dollars (no longer) at work. Probably 10's of billions of dollars of fighters and bombers sitting around waiting for the next war.