I would go look for elf nailpolish and lipgloss for her. Elf is not meaning Santa's helpers but instead means eyeslipsface.com. They sell their products at Walmart, Walgreens and if you watch you can find them at Biglots. The prices in the stores range from $1 to $3 and online they often have amazing deals like fifty percent off, etc... You could probably give all of your girls makeup for very little and even get a magazine subscription if you spend $30 before shipping online. The magazine changes, and if you wnat their deals you sign up for their email or send me a pm because they will sometimes send 2-3 different discount deals per day via email.
Their products will NOT hurt the skin, and some are actually very good for the skin. If Kayla has acne, go to Walmart and get her a $1 zit zapper. It is a clear roll on that has tea tree and other things and it has been amazing. Jess has super sensitive skin, and eczema and very very painful acne. This zit zapper is super helpful and so is their acne cover up pencil with brush (one end is a brush to blend, and I can see why mom wouldn't really like it, but it blends well and has several things that really help heal the acne so you don't hurt/scar.
They also have a matte finish top coat that is awesome and gives a fun new look to any nail polish you have.
You might be able to find a cheap mp3 player for Kayla, and some sites to download free music. I have kept my eyes out in the past and gotten mp3 players for under ten bucks. the most versatile was a disney one that takes an sd card. It doesn't have any memory in it, but I got five 2 gb micro sd cards with adaptors from ebay for ten bucks shipped. I have some with audio books, some with music, one with xmas music, etc.... I get the micro with adaptors because my phone and one of the other mp3 players takes them and they can be used in cameras, etc.....
Why not write down some of your stand-by recipes in a book for Kayla? You could print them and put them in one of those cheap photo books and then handwrite messages or print photos of what it looks like when you are done, and the photo book would protect the pages while she cooked.
For your adult kids, the book I keep mentioning here, the Complete Tightwad Gazette by Amy Daczian will save WAY more than the cost of the book and you could end up saving them hundreds over a year's time. I think that using ideas and recipes I find there has easily saved husband and I twenty to thirty grand in our marriage - and that is a LOW estimate. I have other titles that would also be helpful and fun. Heck, Kayla might even like the make a mix cookbook just because it is different and maybe would give some healthier alternatives to what her parents cook. Sort of foster a bit of fast food rebellion, Know what I mean??
Take a look at the Home Despot and Lowe's websites and/or call the stores to see when they do kids' projects. Usually they are free, the expensive ones here are never more than $5, and the child gets to make something and take it home. The child gets the item, and the experience.
Another thing that might be awesome for the kids would be to figure out how much the Children's museum in Cinci (at union terminal) costs, and take your own snacks one day and give them that experience. It is a truly amazing place and I know husband and I loved it as much as the kids. Step, I think that you would love taking Meggie there in a year or so, and if Jett showed any itnerest, they have some awesome things. He may be a little old, but given some of the issues, it might still be fun. You could do another museum there if it wasn't fun for him. THey have a a special quiet place to go and nurse or take a quiet time with a child.
What about jewelry making for Kayla? Lots of craft places have beads on sale now, and you can get finding for very little. Last year J took some fish hook style ear wires and mini ornaments and made amazing earrings. husband's sister is still wearing her pair regularly a year later because they go with a lot of her clothes and are really pretty. You could go to a thrift store and find old necklaces to take apart too. She might have a ball with that.
I think you are a very special Nana and of course they think you are Santa's special helper - you are a Nana!