Personally, if you are going on in to the night, then I think 1pm is too early to start.
Church service generally takes 30 - 40 mins, (Depends on how many hymns / how long the hymns are / how many readings / how much of a sermon / etc)
If you are having photos at the Church - you need to leave time there (maybe just 20mins if only having a few, and more at the Reception, maybe 40 mins, or up to an hour if you are having them all there).
If journey to the Reception is a 2min drive, you have to double that for folk to return to their cars (often not much parking at Churches, and people might have a bit of a walk to get them), faff about a bit, get lost, stop for petrol, or someone will wander off to find a shop for something, (I'm presuming easy parking at Reception?), some might take their car home and get a taxi or a lift to the Reception. In all, some people won't be at the Reception for quite a bit longer than the 20mins you'd think it takes.
I think the bit where you have 'gelato and cocktails' is the bit which has got longer and longer over the decades. People planning weddings often see this as a 'lovely relaxed time to mingle and chat'. Guests more likely to see this as 'trapped time, starving, waiting for the food' 
. If you have all your photos then, it at least saves the time from the Church, but it is still a long time for people to be drinking alcohol on an empty stomach.
Don't forget, if the service stats at 1, guests will have been arriving since 12.30, and traveling before that. No-one will have had lunch.
Your meal - if you then start at 4.30, will probably take about an hour and a half (Though does depend a bit on how many guests you have - obviously a kitchen can serve 20 people quicker than 200 people). Speeches / cake cutting / photos generally 15 - 20mins (will depend on your speakers).
Then you need to ask the venue what time they need between 'day' and 'evening'. If people need to clear out of room they've eaten in, then return, or are there 2 rooms or do staff leave room set up as it is or just clear the tables.
I wouldn't invite the evening people too early as it is embarrassing if you turn up and the 'evening party' isn't ready for you.
If you are having Ceilidh band and DJ, you need to talk to the band - again about setting up time, and also about what 'sets' they will be doing.
Hope that is a helpful start 
.