This unisex cardigan pattern for babies and toddlers is knit top down. Instructions for both “in the round” and “knit flat” are given for the sleeves, just choose whichever method you prefer.
There is a detailed photo tutorial for the bubble stitch.
All sizes have been test knit and the pattern includes a schematic.

7 sizes are included from birth to 4 years.
Any DK weight yarn is suitable. You need between three and five
50 gram balls depending on size.

I also have bubble stitch bonnet and blanket patterns available in my store.