Arts and crafts for kids probably is the best gift along with instruments and sports equipment to give to children at holiday times and birthday times. I was an only child, my brothers were 13 and 16 years older than me so my mom and dad would buy me craft items and I would sit at my great grandmothers house on Saturday Night watching Lawrence Welk and doing my punch yard project,or drawing cartoons. I honestly believe what you have around your children will build interests in them.
If you yourself gets an art idea, do it with your children. Make their art and their crafts your wall art. Mount it on foam core, place it on the frig with a magnet, buy a clear frame from Christmas Tree Shop or the Dollar Store. When they do a new picture, put it in the frame and change it. You will constantly have new colors and ideas on your walls. You may not be able to keep everything your children do with the arts and crafts, but take a picture and put it in an album. I have homeschooled my children and can not possibly keep every paper, drawing and craft, so I would take pictures of them holding their piece. Make an art portfolio with them and date the pieces. This will show a progression in their skills.
You can cover their bedrooms with wall art. Make a mural type affect and select frames that match their furniture or perhaps a frame that compliments their individualized art. Have fun with this.