WOW! If I didn't know any better, I'd think you were talking about my own sister! Except she doesn't have any kids. But there was one time my dad sent her a check for $20 for her birthday. Which, by the was, was/is the standard gift for each of us kids for birthdays, and we're all adults on our own now. Not only did she NOT thank him in any way-seriously, no note/letter, call, email, nothing-but she also called me up to complain that it was only $20, and that it wasn't even enough to get a DVD without having to put in extra for the tax! WHAT???
Sorry to diverge. OP, I understand the crazy jean, really I do! My DS is 8, and would be overjoyed at a $25 gift card. Like someone else posted, if there was something he wanted that cost more than that, he would graciously say thank you and then quietly plan to save up the rest for whatever it was he wanted, and then send another note saying thank you again and say what he put the $ towards. He likes doing that sort of thing. But most likely, he would beg me to take him to the store the very next day, and would spend it all, and have a blast doing so.
Don't know where your SIL got the idea that a kid can't get something for $25. Maybe she should take my DS with her, he could come home with half a cart full of stuff for that! Besides, I believe you said there were 3 kids you sent cards for. That's $75! Can't they decide on a video game or two that all of them have been wanting and splurge on that? Just CRAZY!!!!!