With extremely sensitive and airborne peanut and tree nut allergies, we've been warned to avoid several airlines who serve peanuts and/or tree nuts as their regular snack. The onboard announcements DO help, and knowing that the flight attendants are aware of the allergy is reassuring. You can request the gate staff to make an allergy announcement as well, and a few will do it, but most won't. That's a really great idea and I'll be more conscientious to ask them to do this on every flight so people have time to get other snacks, if needed.
We also try to bring extra snacks for people seated near us who may have brought a nutty snack and would like an alternative. If I hear someone near me complaining or denying their child their snack due to the allergy, I'll offer them some other snacks. I don't want to inconvenience anyone, and we don't vacation often as a result, but sometimes it's going to happen.
WestJet is our preferred airline because none of their onboard snacks contain blatant nuts or peanuts, they make announcements before the flight, and every single flight we've had with them (save code shares) the flight attendants have asked me for the location of my EpiPens. (They also have some in every onboard medical kit, kudos to them.)
As for the OP, or anyone with allergies flying with an airline that serves nuts/peanuts, I would recommend an early flight, to minimise the allergen residue on surfaces, as planes are typically given a thorough cleaning at night. Call the airline at least two weeks before your flight to inform them of the allergy so they can flag your file and make any announcements or change the onboard snack. Be sure to remind the gate attendant and flight attendant of any accommodations you were promised, such as a different onboard snack. Board early to wipe down the surfaces. Wear long pants and shirt sleeves to minimise skin contact with the seat. Try not to eat on the plane if possible. If you must, thoroughly wipe hands before eating and choose snacks with packaging you can hold onto whilst eating, like granola bars or fruit bars. Have your EpiPens on your person or in the bag under the seat in front of you, not in the overhead compartment.
Have a safe and fun holiday!