I wouldn't freeze whole oranges, except for later use in cooking. The wedges are good for sucking in the summer. You need to watch that the bitterness from the peel doesn't affect the fruit - more of an issue with oranges. Grapefruit - I haven't done it but it should be possible. But not if you plan to serve them for breakfast - when you let them thaw out fully, they are soft and a bit mushy. This is fine if you want to juice them, but not for eating once thawed. If you let them thaw out after they've been fully zested you don't get the pith bitterness. I would only freeze grapefruit if you plan to either juice them or make marmalade afterwards.
A trick I do in summer - I got those ice-cube moulds which are shaped to take a lemon or lime slice in them. I put the slice in with peel removed, so it's citrus fruit only, then pour fruit juice into the mould instead of water. These are fabulous to add to sangria (which is a lovely drink to sip as you watch the sunset, on a summer weekend). There are a range of sangria recipes, both white wine-based and red. I even found a champagne sangria recipe. The necessary ingredient also, is the fresh fruit and lots of ice, so I often freeze the fruit pieces and add it that way. Blood oranges especially are marvellous in this recipe.
Oh, and you can freeze whole passionfruit, but you need to keep them in a sealed container if you have a frost-free freezer, or they lose their moisture. To use a frozen passionfruit, you let it thaw slightly to soften the skin, cut them in half and the insides scoop out like an ice cube out of a tray. You can drop it straight into summer drinks, like a flavoured ice cube. As it thaws out, if not only chills the drink it flavours it. Or you can throw them in a saucepan with chopped apple, sugar and butter to make a passionfruit butterscotch sauce to pour over - well, anything sweet.
Marg