I am putting something together because our church is finally starting weddings again (no real room for them in our present circumstances).

In fact I have mostly lifted what Patrick Williams (@FSSPmusic here) uses. I have been DM'ing and wasn't going to publish anything, but I need more advice. Patrick says:

The seating of mothers and grandmothers is to begin promptly at the announced ceremony time. There will be an additional charge of $50 per fifteen minutes late; after 45 minutes, the fee will increase to $200. It is also under­stood that a wedding ceremony should normally take no longer than an hour and a half, or an hour and 45 minutes if full Hispanic customs are observed, and that singers and musicians may have to leave early if a wedding starts considerably late and they have commitments later in the day. Starting late shows disrespect for the house of God, the dignity of the sacred rites of divine worship, and the time of invited guests, hired professionals, clergy, altar servers and their families, and choir members who taken time out of their day to make the wedding as beautiful as possible.

The pushback that I'm getting to including that is basically that: — it's unenforceable.
— the tardiness may be for a good reason, even if we are talking a much longer period of time (let's say forty-five minutes)
— someone then has to go to the spouse-to-be who is present or the parents and remind them of the policy
— They won't send a check, so you need to collect the fee then and there. But maybe they don't have a checkbook, no cash, insufficient funds.
— the priest will tell you to start the wedding.

I am actually ambivalent about a fee, but Patrick's parish is similar to mine. A Mass is easily a three-hour deviation from the rest of our days: we don't even get to warm up, but we leave up to an hour early, to get there a half-hour or even just fifteen minutes early, and it's at least a half-hour trip back, after a Mass that lasts at least an hour. The trouble is that we're in an in-demand urban neighborhood, across from which is the large park where many city events are held on Friday nights or weekends. The minor-league ballpark is nearby (it's not that much traffic, but it's traffic that means the difference between on time and a little bit late!). We're not that far from the football stadium (the college games on Saturday featuring the local HBCU aren't a big deal, but that's where the neutral-site home games of the University of Tennessee are held, and there are concerts in summer). Accidents are a frequent concern.

My attitude is that a late couple isn't my problem. I know that musicians here have forced parents to pay up in the first place and that that was an exception; their usual policy was that the parish was to receive payment in advance, not to wait until the day of the wedding. I don't see how a late fee known to be a part of the policy is different. Either pay, if you can't be on time within a reasonable buffer period, or the musicians get to leave (keep in mind too that, well, we can't start without the couple, the priest, or the organist…and in my case, we have always started on time with all musicians or with the straggler showing up within Patrick's buffer period, in my four years here; only once or twice have we had fewer than expected — but everyone necessary to do the propers was on time, which sort of gets to my point that a fifteen-minute buffer afforded to the schola/choir doing the TLM, where the wedding precedes the Mass, is actually unnecessary in most cases)

The local parish that would have similarly high standards of sacred music does not have a late fee. They simply say that weddings must start promptly at 11 AM or 2 PM on Saturdays or on Fridays at 6 PM, whatever time is schedule of the three available. They do not indicate what happens if a couple is late. The pastor does not list the possible consequences, but there's got to be one, right? (I just emailed to ask.) I can't find too many parishes with published wedding policies including the music one.

Any thoughts? I want to be able to say to the pastor "this is what others do, this works, I don't want to reinvent the wheel, and I want something that no one can plead with you to not enforce".

I mean, I'd be fine if the fee is just considered a donation to the parish and not necessarily income for the musicians, but I want there to be a real consequence.