Break between wedding breakfast and evening reception

You could end the afternoon do with the cake cut. Put on the agenda "cake cut 4pm" then "chill out time" from 4-7pm

Well you'd just put "there will be a break after the wedding breakfast until the evening reception at 7pm"

Or, as everyone is local, just tell them in person and have whoever is running your day make an announcement when it's ok for people to go.

"There will now be a break until the evening reception, which starts at 7pm and will be held in ... Guests are welcome to stay on site or return home if the live nearby until that time. We hope to see you all later at the reception"

The cake cutting idea seems like a good "end point" for the meal and stuff

There may not be quite so long afterwards as you anticipate, for an 11am wedding - allowing for 10 mins late and then for everyone to filter out of the church you wont be outside the church and mingling until 12.00, maybe a few shots at the church then confetti - I assume that you are walking from the church to the venue which you wont be walking until near 12.30.

Then by the time you have walked around and gone to the loo and everyone else arrives you wont have everyone there and ready for groups (if you want them ) until 1.00 - then allow 1.5 hours for mingling - drinks - photos and call to sit at 2.30, depending in the nature of the service and how many guests you have - allow 2 hours for this and then another 30 mins for the speeches which brings us to 5pm. And if you tell people 7pm eve start there will be people who arrive at 6.30.

To allow for a more informal relaxed no pressure time after the wedding then start the call for the meal 30 mins later at 3.00, giving you 2 hours on arrival at the venue which will still fly by.