I'd budget your normal weekly grocery budget...and I'd shop with a few tricks.
1. Stick to one "fat" for the week - for me, it's normally butter. We use it to cook with, bake with, and spread on bread/toast. No need for oils that I'd use a few TBs of and toss...
2. Buy salt and pepper...and then stick to seasoning packets or jarred sauces to cook. Don't but 10 types of spices and/or herbs - again, you'll just toss most of them.
3. Have items you can cook multiple ways for variety - eggs are great to buy (scrambled eggs, fried egg sandwiches, french toast, frittatas, and omelettes give you options for all 3 meals with one item

...bacon is another great item (served along with or in eggs, made into a club sandwich or BLT, topping or add-in for tons of salad or on top of baked potatoes/french fries

...you can also use the bacon fat if you get sick of butter to cook items in...
4. Buy more fruit than you expect...it's so easy to serve and you will go to it more than veggies...
5. Buy ziploc bags - you can pack stuff for parks, hold leftover items, etc...
6. Buy paper plates/cups/napkins - no one wants loads of dishes on vacation - simple and easy is where it's at

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