Welcome to KH and congratulations on the coming baby!
Velvetspun and fun fur wouldn't be my first choice for a baby, or anything really, because I hate knitting with them, but if you like them then go for it!
The biggest problem you'll have I think is finding a pattern for a baby using these yarns. Most baby patterns are knit with finer yarns.. like sport, DK or worsted weight.
Here's a site that has lots of baby patterns..I've linked to the hats, but here are other patterns, too. Maybe one of them is a bulky hat.
ETA: I did find a hat on the Lion Brand site for that type yarn. You can see it's pretty bulky. Also not a bonnet.
And these are for bulky yarn so they might work.
You could also knit a rectangle, fold it in half and seam, then add ties for a simple bonnet, too.