Breakfast at a café
Toast, fruit, egg, or porridge are usually enough, when those foods fit the diet and allergies. Ask for it plain.
Ask for plain
You can bring a banana in your bag if the menu is uncertain. Café breakfast does not have to be the day you branch out.
Butter, honey, and a cheese sprinkle are easy add-ons to refuse. Plain toast or plain fruit is closer to home.
What stays off
Egg stays off if the diet is vegetarian or egg is an allergy. Bread and oats stay off if wheat is an allergy. Cheese and yogurt stay off if milk is an allergy.
If the only safe choice is the fruit you brought, that is breakfast. You do not have to order a meal to belong in the café.
The pace
They may finish before the coffee does. Let them be done. A short café meal is still a meal.
Sit where you can see them chew. A busy café is a place to watch, not a place for a first food.
A sentence you can say
“Plain toast, or the banana we brought.”