L.G.
If you don't start now, it is going to be ten times harder in the future. I was working outside the home when I had my 7 year old, she has stayed at her grandma's numerous time while her father or I traveled. She is SOOOO flexible now. I see so many other children just FREAK out about being separated from their parents. I have a two 8 year old nieces who cannot handles sleepovers with us or friends b/c they have never been away from Mommy. If you wait until she is older, it will be more difficult and maybe even impossible.
I now am a SAHM and have a 2 year old who has never left me or Daddy's side. About 5 months ago, we enrolled her in a Mother's Day Out program and she had the worst separation anxiety of any child in the class.
And ENJOY your vacation without obsessing about your daughter. When you return, she will never remember you ever being gone!! I went on a cruise and another couple who dined with us nightly just did not enjoy themselves b/c the mother couldn't get over missing her two boys which brought her husband down too (don't get me wrong, I miss my kids when away). She ruined her vacation b/c she couldn't get over it so ya gotta try and focus on you and hubby and be grateful that you have relatives to care for your girl.