Am I training my child to lie?

Today is Diane's 50th birthday. She has been a great friend, through work for many years. She and her husband are like another set of grandparents to my gurlz.
Don planned surprise party for Diane tonight and we were invited. To assist in the 'surprise' and because I wanted to do something special, the gurlz and I brought breakfast over this morning. It was wonderful. Diane was just ready to brew her own coffee (something she had not wanted to do on her birthday) and we came in with homemade pancakes, coffee, jam, champagne and gifts. We had a wonderful couple of hours and even swam with the gurlz. Then we left as we needed to nap before we went to a housewarming.
At about 4:30pm Diane came home from a day of pampering (hair, nails, facial, shopping) to a backyard of friends. As she stated 'some of you are very good liars!' We left a little before 10:00 pm and it was a wonderful time.
Is this lying justified? I mean, technically, the big gurl didn't lie. I had told her before we went that we were going to a housewarming party at another friends so...
I think it's okay, its just if you think about it too much...
We had a marvellous time and Diane was very surprised and I met some wonderful people. The gurlz each picked a favourite boy and played with them for over an hour. Thank you to Craig for swimming for two + hours with the big gurl. I was still chilled from the morning dip.
On the knitting front, the first sock for Dad is on the needles again. I also knit another pattern repeat on the baby blanket, cause I wanted the needle for the socks, but realised I risked ruining the blanket and really I need two circulars, so I am going to call Susan at the Knitting Habit and get her to set aside a couple of Addi Turbos in 4.0 so I can pick them up next weekend. I really should get the sock done first but, we will see.