Is this assault or am I overreacting?

I'll make it clear first that I am not planning to take any legal action. But I do hope this discussion brings light to what is becoming common in the UK and that people with the same experiences do not feel alone.

Situation:

I was walking in a town centre when I turned into an alley and felt a squirt of water, I looked around and saw 2 girls (15-16 ish) trying to conceal what looked like water pistols and hurried away. I then realised they must have sprayed water on me.

As a soon-to-be father, I thought about how reckless child gangs have become recently. While they didn't strike me as a "gang", I felt that children should know that wrongdoings come with accountability.

By the time, they have already hurried off ~20m into the high street, so I planned to catch up to speak to them. At first, I can see them glancing back. After a bit, they seem to have forgotten about it and started shooting water at each other.

It is worth noting that, while they were doing this, they were all jolly and loud, which contrasts with how they tried to conceal their actions after shooting me. This assured my assumption that they targeted me.

I did manage to catch up eventually and we had a back-and-forth conversation, we were all very calm, but they denied everything.

Escalation:

This is when their father appeared (previously not with them). He took the water pistol from their hands and shot me in the face, saying I "should not be picking on little girls". I was in absolute shock and didn't know how to respond. The family just walked away when I tried to make sense of everything.

The question:

Was the father right? Am I overreacting? Or are the girls causing an offence / nuisance to the public that warrants my actions?