Kate, in a reasonable world you'd be right. And in a reasonable world busybodies wouldn't be trying to interfere in what happens between consenting adults in private
Unfortunately "payment" in Irish law covers anything you can think of.
The definition of "sexual services" will probably be as wide as possible, certainly at the beginning unless the Attorney General steps in to narrow it. I don't expect her to be minded to do so, they'll probably leave it to the courts. The government will certainly aim for it to include "massage" and BDSM, so basically it'll be whatever the judge says it is until proven otherwise.
The PayPal approach has some problems:
First, in Ireland there are only two ways to get money
out of a PayPal account, either a) send it to someone else which is of limited use or b) transfer it to a bank account. You can only link a PayPal account to one bank account at a time, and thanks to our wonderful anti-money-laundering law that links back to your real name and address.
Second, Paypal (being run by American Prudes and under pressure from the US DoJ) will not deal with anything related to "sexual services". It's in their T&Cs. If they get so much as a hint that the account holder is doing anything remotely sexy, for example by their own monitoring or a tip-off email or anonymous phone call, they will suspend the account immediately. It is practically impossible to get the account unfrozen. Any money in the account will be lost, you'll never see it again. The bank account can also be frozen in some circumstances.
Third, any other email addresses linked to that account will also come under suspicion and any linked accounts are likely to be frozen as well.
Fourth, you can't set up a business PayPal account without a VAT number, and anything remotely like massage or coaching will sooner or later get the account frozen "temporarily" while they "review" it and make you send in copies of training certificates etc.
Trust me, you really really
don't want to go down the PayPal route.