First Solo-Playdate Anxiety

    I'm having some serious mommy guilt right now, and questioning my judgement and parenting skills.  Quinn is on his first ever solo playdate, without me!, and I'm suffering with my decision to let him go. 
    Last week, I accepted an invitation for Quinn to go over to a classmates house for a playdate.  No problem, right?  The little girl had been to our house a few weeks ago, had a nice lunch and some fun playtime, and we've been to other playdates at other classmates' houses and they've always played well together.  She is a wonderful little girl, so sweet and precocious and friendly, and her mother is always very warm and inviting when I see her at their school; she frequently offers to help me as she sees my hands are full with three kids.  Plus, they live only a few blocks away from our house.  It occured to me on the drive to their house today that, wait a minute - how well do I really know them?  Sure people may appear nice on the surface, but what if I'm completely naive and miss something?  What if they have a torture chamber in their basement?  What if they skip town with him and I never see him again?  Should I have been to someone's house before leaving my child there?  Checked for hidden dangers or red flags or proper childproofing?  Does this make me a terrible mother, maybe I didn't do my due diligence before sending him to a new place?  What if he gets there and he's scared or sad to be away from me?  What if my assurances to him about his safety aren't true?  And I can't help but loosely remember a quote from "Girl with the Dragon Tatoo" - something about the urge to offend someone being stronger than the urge to flee a sense of danger.  Should I have had that talk with him already, about the inappropriate touching and not keeping secrets from us?  Ugh, I've completely dropped the ball!
    And am I really ready for him to go over to someone's house without me?  There are other friends whose houses I would not have any concern sending him to, places we've been more time than I can count; maybe I should have practiced there first?  And it's not even that I have any reason whatsoever to be concerned about the current playdate - I guess I'm just having some separation anxiety myself.  
   We pulled up to the house, and I went around to get Quinn out of his seat.  He suddenly realized that I wasn't staying this time, and he was understandably a little anxious and started the "But Mommy, I'll miss you" and "I want you to stay, too" as we walked up to their door.  I assured him that he would be perfectly fine, and that we only live a few blocks away, and he can call me or come home anytime he's ready.  I nervously reminded him to be a good friend and remember his please and thank you's.  We were barely able to knock before the door swung open, and the little girl was beaming at his arrival.  I walked him inside and was met by the mother, a big grin on her face and super relaxed and inviting.  It was warm and clean in the rooms I could see, and it seemed open and bright; nicely decorated, not cluttered, comfortable but orderly.  Quinn threw off his coat and shoes, and ran to play with his little friend, so I could tell that his anxiety had faded, but I had a heavy heart as I smiled back, finalized the details of his return home, mentioned that he might be scared of their dog (which she said would stay on their back porch, no problem), and slowly walked back to the car (where the twins were waiting and asking why they couldn't go to play, too).
    I brought the twins home and fed them lunch.  We read three books, changed diapers, and sang a couple songs before laying them down for their naps.  They went to sleep immediately, peacefully, both tired from restless nights and having been under the weather for a couple weeks now.  I made myself some lunch, surprisingly ate it while it was still hot!, and then slowly realized how quiet the house is.  Part of me is a little excited for some time to myself - it's rare to have some time alone in the afternoon, when I feel more motivated and think I might actually be able to accomplish something.  Even when the girls are sleeping, most days I tidy up the lunch things and do a little dinner prep, but then I play with Quinn and truly enjoy the one-on-one time we have together.  So then the other part of me speaks up and misses him being away right now, and starts to question whether he's okay over at his classmates' house, whether I made a good decision to let him go...  So instead of being productive (not that writing on this blog isn't productive!), I find myself just killing the time until I see him come down the street, up onto the porch, and back into our home, and into my arms. 
     I know that he's <probably!> perfectly fine where he is, and is <probably> having a pretty good time right about now.  And I also know that it's <probably> just my insecurity and inexperience making me feel guilty about letting him go.  I know that the first time leaving him at a friends house will be the hardest time, and that it's a totally normal thing to and will happen more and more frequently now that he's getting older (5!).  For now, I'll just keep looking out the window until I see them walk around the corner (oh no, it's snowing!  Did I dress him warmly enough?  Will he be cold?).  Waiting to hear his footsteps again...
     Sigh...