Hi dinkydee - Just curious, why do you say you are failing at P3? What part of it is causing you problems?
I notice that your breakfast sounds pretty sparse, you should add some fruit and protein - is there enough in the yogurt? maybe add some nut butter. Are you using MFP to check?
Don't be afraid of P4
To start, try to keep it simple. Have a P3-type breakfast. Grain, dairy, fruit, fat.
That could be oatmeal, with yogurt or milk, some fruit, --or ---egg/toast with PB, fruit, milk or yogurt. Should be doable at restaurants
Lunch - protein, veg, fat - so a Chicken caesar salad, or a regular salad with full fat dressing, with some chicken, shrimp? maybe some cheese. Tuna salad with mayo on lettuce?
Dinner - protein, veg, carb - so any lean protein, veggies just like on P1/P2, and a good carb (potato, sweet potato, rice, quinoa).
You can have your IP bar/drink for a snack, or you can have fruit, or almonds - maybe take some of these with you to keep on hand.
Good luck, and don't stress out too much, Vacations are supposed to be fun