Thanks. I've re-read your post several times and my best advice would be to try to dilute your husband's ability to influence your daughters by interrupting his visitations every week or so during the summer (if possible) and get them alone with you to obtain a subtle, casual debriefing about what they did
during the prior week. You will find that they will more readily recall things their dad said to them in the prior few days and this action will put your ex on notice (you won't have to say a word), that he won't have complete and unrestrained access to the girls' thinking and development of their beliefs. In other words, he will automatically read your interrupting of the visitations as monitoring what he is saying and doing. And, as I said, you could curtail the visits if you got repeated hints that he was undermining you. You are in a position to limit this on legal grounds, but mostly custodial parents dawdle, procrastinate and can undermine access in more passive ways and the noncustodial spouse really can't do much about it except complain. This would then set you up to more immediately 'call him' on stuff he does e.g., "I'm concerned that you are making promises to the girls you have no intention to keep and which you haven't obtained my agreement and consent." Another key message is that to deal effectively with individuals who are narcissistic, is to set clear, firm and absolute limits with them and communicate what these are and why you are creating them; and then, make sure you do not engage them in debate, endless explanations and justifications, etc. Now, here are a couple of quite good books on how to manage the behavior of someone with narcissistic personality disorder more effectively.
I hope this information is helpful to you. Let me know if I have overlooked any aspect of your original question. Please click on the green Accept button at the bottom of the screen. Thanks.