Is a blanket stitch doable for first-time knitters?
As mentioned in 111's answer, a blanket stitch is not a knitting technique to create blankets.

The biggest risk in your plan is time. Babies often decide they want to see the world before doctors decide it's time for their birth. You should finish the blanket at least 2 - 3 weeks before the scheduled date.

If you are quick and comfortable learning knitting, you can use any stitch or technique you'd like. I found Youtube videos extremely helpful and did learn complicated patterns that I wouldn't have understood otherwise. But you should experiement and create small test pieces of your blanket before knitting the whole thing and then realizing that the corners roll up and it's impossible to actually use it as a baby blanket.

And that's where the time requirement comes in: If you don't have experience with how certain knitting pattern react, you need more time to experiment. You can knit an entire blanket with just stockinette stitch, but it will roll up at the sides and won't lay flat. You could knit it with a ribbing stitch (usually found in knit cuffs, because it prevents rolling), but you'll need to knit it wider than intended because the finished piece contracts some and is narrower than it was on the needle. There are very beautiful and easy cable patterns, but if you cannot "read" the stitches on your needle it's very easy to make mistakes.

Additional hint: the "continental" knitting style is faster than the "english" style, but they both produce exactly the same patterns by the exact same needle movements. I highly recommend learning contonental style from the beginning.

If you fear you won't be able to finish a knit blanket in time, crochet it instead.