Additional boutonnières and corsages

No, you don't HAVE to, but how much are they quoting you for boutonnieres? Ours cost $10-$15 each, so when you say "less expensive," I'm trying to figure out what your starting point is. For any females, I don't think you need a full corsage (those do tend to be more expensive; ours were $35), so I would just plan on small boutonnieres for everyone if that helps save money.

You don't have to, that's totally up to you. If you do consider artificial flowers you'll need to check with your florist first to see if that's something they even allow. If most of your floral is done by them and the fake flowers look bad then that reflects back on them, so most won't allow you to mix like that.

I think it's personal preference, and of course, budget-based.

We are having corsages or button holes for both dads and mums, plus my fiance's grandma, but our single reader and our MC are not.

We're not doing additional for readers. We're also skipping ushers so we don't need those.

No, I don't think anyone necessarily has to give boutonnières or corsages for readers and ushers. I will advise sticking to your budget.