I think I got this link from here. Lots of different topics on money, definitely targeted to kids.
https://www.bluetreesavings.com/If you have a chronic saver, you've probably solved or avoided the biggest issues of that age. DS is a good saver, but constantly talks a "good game" about spending everything he has. Thank God something has stuck, and despite his talk, he spends only some of the time. I would suggest that your DD may benefit from some targeted spending--savings with goals in mind. Of course, not the whole thing, but perhaps something that she talks a lot about; to add to the endorphin rush of achieving a goal. DS, for instance, saved for his Nintendo Switch. With grandparent money, it took a little under a year, but he (with no internal monologue) would talk himself through spending temptations, knowing he was x% toward the Switch.
Here are some parameters of how I have taught savings:
Distance is good. We used a 3-part spend / save / share bank since he was counting and identifying coins. When out shopping, if he didn't bring some spend money, he doesn't have money to spend that time. (Older kid option: we have offered to "loan" him money for a purchase, with a 10% charge. The item is not his until he pays it. Intended as credit card training)
Even better distance, he has a savings account. He enjoys the formality of "adult business," filling in deposit and withdrawal slips, talking directly to the cashier, etc. With no debit card, hours are limited, so we most often go on Saturday mornings.
Rather than worry about actual interest, the "bank of Dad" pays all savings (save bank and savings account only) 10% a month, to accelerate compounding and achievement of goals. He delights / cackles / taunts me when he adds to savings, knowing that interest is coming. At some point, this will have to tone down; I don't have my exit strategy thought through yet, but it will probably be a reduction in frequency, to draw out those endorphin moments toward real life experience.
As an example, this year grandma and grandpa gave him a $500 check for Christmas, to be put toward summer camp. He asked me if he could put the check in savings while he researched camps. I said yes, with a couple caveats: he couldn't leave the money in his account for long (summer camp books up) and he could only spend his summer camp interest on summer camp--it's our way of giving him spending money. Only, he has "earned it." He already has the camp picked out, so it will just be a month or two. But as something he is being led too (he loves travel, but is not outdoorsy) the savings aspect has added to the anticipation.
DS has also expressed interest in stocks, and even done some cursory research. But he has not mustered the attention span to get to an actual purchase, even just though my established taxable account. He knows I am very interested in stocks, and that interest has provided some significant luxuries / experiences for our family, including FIRE. (I have said this explicitly to him)
Hope these details help inspire!