Don’t worry too much about the tension - as it’s a blanket a couple of inches here or there won’t make any difference.
If it helps, I used a Turkish wool with the following tension:
22 stitches & 30 rows = 4” (10cm) square.

Whatever wool you chose I recommend something which is machine washable (babies don’t take more care of delicate wool!)

Some people have found that the ends don’t sit flat enough for them, others haven’t found it a problem. If in doubt, it might be worth working the moss stitch rows at the beginning & ends in the next needle size down.

(Apologies for the HUGE delay in uploading this pattern and any inconvenience it may have caused. If there is anything that doesn’t make sense please just get in touch.)