The birthday wishes

One day, when Taran and Morrow were 4 1/2 and 2 3/4, respectively, they were out digging in the garden and they found a package. It was wrapped in bright paper - which was very strange, since they had, as I said, just unearthed it; it was entirely undamaged, a cheery yellow with a sparkly orange ribbon, not even ripped a little. In fact, it looked just like a birthday present - Taran was especially aware of this, since Morrow's birthday had just been a few weeks before, and he was eagerly looking forward to his own. Tied to the ribbon, tucked under the bow, was a note, which read: "For Taran, Morrow, and any others. With much love, from Grandma Weathercolor."
So Taran and Morrow brushed the rest of the dirt off of the package (which hardly seemed to have any on it at all) and took it in to Mummy.
"Well, children, it looks like your Grandma Weathercolor was quite serious when she said she'd make it up to you for not being able to come to either of your birthdays this year," Mummy said, hopping up and down. "You take one side, Taran, and you take the other side, Morrow," she said - and she had them each pull on one side of the ribbon. Then she lifted off the lid, and inside, just fitting the bottom of the box, were two cards. The first one said, "Good for one wish, for Taran Weathercolor, with love, for his birthday." The second one said, "Good for one wish, for Morrow Weathercolor, with love, for her birthday."
"What does it mean, 'and any others'?" asked Taran.
"I suspect it means in case you have any brothers or sisters," Mummy answered. And she put the box up on a shelf in the kitchen. "So, are you going to make your wish, or do you want to wait and think about it?"
Taran and Morrow both opted to think about it, so they handed their cards back to Mummy, who put them up in the box for until they were ready. The rest of the day, as they were playing, they discussed various options; but when they went to bed that night, neither had yet decided what to wish for.