My friend's DD has just started primary school and has been invited to a little boys house for tea. My friend is unsure what to do, in her words, she doesn't know the family from Adam. What have you done in this situation?
Well the only way to get to know the family is to accept these sorts of invitations.
Tell your friend to use her judgement and common sense and accept the invitation, but mayb offer to go with them from school to the house so she knows where the house is and can feel more settled. Then she can leave he DD there for a few hours and pick her up.
It's fair enough to say DD isn't great about going with people she doesn't know, so is it okay if I come too first time - you can add that you won't stay if she's okay. I always did that with DS and nobody ever blinked.
I took a deep breath and let DD go on playdates in reception. Parents collected her from school and we picked up later. Most parents I knew to at least say hello too and make small talk with in the playground, but often that was all.