My sister and her 2 daughters were recently in a resort town near my home. (I live 300+ miles from them ordinarily.) My sweetheart and I I took the day off from work and met them for a day of fun on the beach. It was a fantastic day - we went to the ocean, played mini golf, waded through tide pools and went to a baseball game.
I also felt as if I needed to be especially aware of the balance of time I gave to each of the girls, my sister and my sweetheart. Oh yeah, and myself. It was my vacation day too!
For example, when my sister and I stood side by side and cradled her kids (aged 7 and 4) as the waves crashed over them we took turns with each child - so they both got their desired wave time with mommy and aunt CF. When we played mini golf, the four-year-old melted down, and had the emotional vocabulary to say that she was jealous because everyone played mini golf better than she did. My sister and I gave each other non-verbal signals and it was decided that I would be the one who quit the game to "coach" the little one to a place of increased confidence. Later, when playing in tide pools, the older one had her foot sliced open by a shell, and it was similarly decided that mom would be the one who sat back and staunched the bleeding and soothed her oldest daughter's sadness.
Knowing when my nieces or nephews need their parents to help them through a tough time - or to enjoy a really fun activity - takes time and communication. And being able to negotiate my place in their lives - as cheerleader, helper, or tear wiper, or really fun aunt - takes a similar amount of time and carefulness.