Although no she shouldn't be dictating when he takes them.
I've read threads on here from single parents who are the children's' main carer and can understand why the main carer may have concerns.
I'm not saying this implies to the op.
Times when one has met someone really quickly and they've moved in very quickly together. Adults do what you want, don't bring those children and I would support the main carer.
I mean come on just some of the stories about all the man/womanchild is enough to say hang on a minute. Maybe not.
The extra spending should only be a concern because he thinks it is a concern. And he's not doing it because this has been mentioned to him. The money he gives is for the children. But it normally gets pooled into the family pot. I mean, come on who is really going to work out how much should go towards the rent/mortgage. If you do, mate give me some ideas because you seem to have loads of free time, what's your secret?
So asking him to get her pads in itself isn't unreasonable. Regardless of who he is.
It goes back to what's in the best interests of the children?
Forgetting everyone else involved, what is it that HE wants to do. He's clearly one of the good uns, not only does he pay regularly he pays more.
If he is genuinely happy to take them elsewhere, then he can make proper plans. If you can rent somewhere for the week cheap, then for a weekend on a regular basis it should be doable. In the warmer months even easier, let's go camping.
If he's not then he needs to look at how things can change for the benefit of the children.
Same with the shopping or whatever. If he is happy to do this, then that's his choice. He might be happy to do it some of the time, then he needs to let her know. If he doesn't want to do it anymore, then he has to deal with that. Maybe he's doing it because he thinks it's a nice thing to do.