Baby romper

I am a bit inept when it comes to pattern modification. I am trying to finish my wips, but suddenly I know a couple people having babies (or just had). So the next project is going to be this.

I am going to make the 0-3 month size, but I would like to use 5 buttons instead of 8. Which rows then should I add button holes on?

You could space the buttonholes 21 rows apart starting at row 3 and ending at row 87. The buttonholes would fall on rows 3,24,45,66 and 87. If you want to place them all on RS rows, you could move them to something like 3,23,45,65 and 87.
Do you think this is going to be enough buttons so that the romper closes without gapping at the front? That would be my concern.

hmm… I never thought of that, maybe I should just make it according to pattern!

Is it because you have 5 buttons you wanted to use?
I agree with 5 spaced out rather than 8 the front might gape, but possibly 5 in almost the original position, maybe spaced just a little more, could be enough if the bottom section of the button band was sewn closed?
One of the examples has 7 buttons beginning a little higher on the button band than the example with 8 - so not more spread out.

How do you feel about “after thought button holes”?
I used this method when I wasn’t sure exactly where I wanted buttons, or how many I wanted.

I just thought it looked better with fewer- but anyway, when going through the pattern, I realize there are raglan sleeves- but afterward, it looks like there are a lot of yarn overs- won’t there be a lot of holes??? It doesn’t even say yo, it just says yrn, which I assume means yarn over? Am I wrong?

Yrn is yarn round the needle, a yarn over usually after purl sts. For this romper pattern it’s a plain old yarn over between knit sts in order to increase the stitch count and make the eyelets that you see at the raglan lines. Just bring the yarn strand to the front between the needles then over the right needle to the back. That’s it.
The yarn overs for the buttonholes
K2, yrn, k2tog, (makes a buttonhole)
are noted in the pattern on rows 3,15,27 and then in the: *NOTE: Buttonholes on rows 39 -51-63-75-87