DS is 5 and has ASD, anxiety and sensory issues
After the initial winding down after the end of term (DS hates school and gets very stressed) we were having a lovely, calm and happy holiday...until we started meeting up with people.
We've had 3 social occasions (a party and 2 play dates - 1 with a friend from school at home, another in the park with my friend and her younger DC) and DS has been angry, oppositional and aggressive before each - I'm assuming anxiety. And ridiculously hyperactive afterwards - I'm assuming overloaded.
He's known 2 days in advance about what we are doing (asks a ton of questions but I only tell him this much or find it makes things worse) I have prepped him each time briefly about what will happen but I have no idea how to help these behaviours or what I believe is the cause behind them (I could of course be wrong)
I am trying vitamin supplements (omega 3, a multi vitamin and have ordered magnesium), we're using essential oils, calm music, we have a calm area available, trying to meet sensory needs, herbal tea, looking at whether diet might be a problem...I feel like nothing I try is making any difference...he literally cannot keep still after these events for the entire rest of the day, he refuses/is completely unable to talk about how he feels about any of it 
Any advice very much appreciated