Ex-p hasn't been honest with me about holiday with DC

[WishIwasanastronaut]

Just a quick one - DCs are in their first holiday with ex-P. We separated due to his aggression and cannabis addiction.
DCs seem to be having a great time. We hAve spoken every day on phone.
Just spoke to them and DC1 told me that xxx had been smoking (cigarettes) in the car. Disgusting obviously but easily dealt with in a quick chat with ex-DP.
However, I sm really angry that I had no idea xxx was actually going on holiday with them. I expect ex-P didn't say anything to me as he is a chain-smoking, cannabis-smoking, heavy-drinking mate who I don't really like being around the DCs (although he is a lovely guy - it's just his lifestyle choices).
I have had a tiny bit of involvement with SS around the time of the split (another story). Should I tell them that xxx went on holiday without me knowing or should I just have a quiet word with ex-DP to fully inform me next time? I guess I have little influence on who he chooses to spend his time with.

[TheHouseOnBellSt]

I think you should tell SS. It is in your interests to be completely honest and it wasn't your fault. Your EX cannot be trusted.