Hi, Rosie. Welcome. Unrealistic? Who knows. It all depends on how fast you get the hang of knitting (some crocheters, like me, have a hard time with learning to knit, others don't), what pattern you use, how much time you have to knit, etc.
I'd suggest getting some U.S. size 9 or 10 needles, some inexpensive (I'm thinking RHSS), light colored, wosrted weight yarn and watch the videos here if you don't have an IRL teacher and go for it.
Remember that people here take the "help" part of knitting help very seriously and will help you out whenever, however possible, and often more quickly than you'd expect.
Congratulations on the new grandbaby!