It can be particularly tough for a nanny to find an appropriate gift to give a parent who seems to "have it all." However, if you have a good relationship with your employer it is worth the effort to make a gesture of appreciation. Good nanny jobs are a treasure for all involved and fostering kindness and respect is always a good example to set.
So the question remains, what make, or buy for someone who has significantly greater means than you do? My answer is generally to avoid buying and turn instead toward the making end of the spectrum. Making something allows you to showcase a particular skill and is especially meaningful if you can involve the children in the gift's production.
If your skills are cooking or baking, go for it! If you have a few special recipes you make for your charges consider printing or handwriting a mini cookbook of those recipes for days you are not there. Sometimes the simplest recipes might be the hardest for a parent to guess without your special instructions. If Mary Jane likes the way you mix up hot cocoa with just the right amount of mix, write it down! If you have a special way of making a treat that is healthy and low in sugar, write it down! Whether typed up in a fancy font and printed or written on pretty recipe cards these little recipes may be invaluable someday either on a weekend. They may even serve as a snapshot of what the children loved to review someday when they are older.
If you skills are the needle crafts, such as knitting or crochet, there are lots of wonderful free patterns available for small gifts. I love to crochet and find great patterns on the Lion Brand website. If the children are five and over many times you can teach them to help with a small part of that project. If the children are old enough to put beads on a string and not in their mouths, you may be able to help them pick out a couple strings of silver, glass, or crystal beads to put together a very special piece of jewelry for mom. They may even enjoy making the beads out of polymer clay that hardens when baked. As long as they are poked with a toothpick before baking they can be strung onto jewelry elastic after they have hardened. Gifts from both Nanny and the kids are often greatly appreciated.
If you are an artist or photographer, parents would usually adore a portrait of their child. If you don't consider yourself particularly artistic or crafty there are lots of kits available in craft stores for under ten dollars that can be used to create something memorable such as a plaster handprints with young children, or mosaic stepping stones, or painted, durable picture frames, or Christmas ornaments. These don't require artistic skill on your part, only your patience and supervision. Don't forget, after the children have done the painting seal the craft with ModgePodge for durability and date it with permanent marker. These keepsakes will probably be treasured for a very long time! As long as you are making easy crafts you could also consider allowing the children to make multiples to go to grandparents or other family members. This can be a big help at the holidays, alleviating some of the parental gift giving stress. Anything that serves to reduce their stress you know will be appreciated!
Whatever you choose take the pressure off your mind and realize that these gifts are primarily tokens of your appreciation. If you are running out of time, money, or both don't panic! Simply purchase or make nice holiday cards and help the children sign them with you. Use the opportunity to teach the children in your care that the holiday is about sharing loving-kindness rather than stuff and that they too can be givers.