May a dinner guest invite more guests?

by Gabriel
(San Antonio)

Our niece, who is in the Air Force and stationed in Las Vegas, called on a Friday to let us know that she and two colleagues were driving down to San Antonio for training. She wanted to know if they could rest at our home before checking in at the base. "Of course," we replied. We were already planning a small Easter feast for ourselves, our daughter, and my parents on Sunday afternoon. After checking with my mom, we invited our niece and her colleagues to join us.
They arrived on Saturday and spent the night. On Sunday (this morning, in fact) while my daughter and I went to sunrise mass with my parents, they got their gear ready and went to the base to check in; they intended to be back in time for dinner.

Later this morning, our niece called to ask if she could bring three more soldiers to join us for dinner. We regretfully informed her that we had not planned enough food for that many guests.
Were we less than generous in rejecting more guests?