Ah, the world we live in.
Not a stones throw back there is a thread about this same length where the stepmother was told she was trying to be too involved and that shes just a step parent and should not have any delusions of parenthood and here we have the exact opposite message sent. Its little wonder blended families are so complicated.
When I replied initially, I did ask if there was a specific request for souvenirs. I see now there was not. It was a hypothetical question. I think we are trained by so much time on the internet to read more into things. It never occurred to me that nothing had happened to prompt the original question. I stand by my answer though. In short, No. If one or both of my children is going on a trip with someone or some people that close to them, Id only send money if one or both of two situations is present. 1) If I want them to bring me something back or 2) If I ask someone to take them with them on their vacation.
I dont have this situation with my biological children going off with their father for reasons many of you know, but my daughter has gone on two trips with her Godparents. I did not send spending money with her, but I also didnt expect her to bring me anything. They also asked me if they could take her with them. Had I asked them to take her on the trip, as was the case when their daughter traveled with me a year or so later, then I would have sent money. I had a trip planned for Spring break and they asked if Id take her with me. I had to switch our room reservation to a suite after agreeing to take her, but it was no big deal. They did though send money for her to eat, shop and pay admission to the places I told them I had on our itinerary. Had it been my idea to take her, I would have covered all of that.
OP, it sounds like you are concerned that if they spend money on their family back home, they wont have enough for what they want. It also sounds like you think the family back home should get souvenirs from the trip. Its not a necessity though. Either way, it is okay for you and their father to monitor that and guide them the same way you would if you see them picking out something you know they wont want in an hour. But then I parent a toddler and an elementary school age child. I dont know how old the children involved here are. It also sounds like you are willing to spend additional money if it comes to that.
Ive been a stepchild and a stepparent and Im certainly not here to analyze someone I dont know and try to tell you what you have in your heart towards those children. Even if you posted something about them in the past, our hearts grow and change with time and I know from experience bonus children grow in your heart with time as things settle. I remember the first time I cried when my stepson went back home to his mother. I was so glad to have reached that level; that he had grown in my heart to the point I was heartbroken to see him go home.
I hope you all have a great trip.