Day 13 both dogs very eager, showing all signs. we have had 2 slip matings, about 30minutes after the 2nd slip mating she leaked quite a bit of clear fluid.
Day 14, we never had the dogs meet as to give them rest.
Day 15 now. Still very eager. They've had 2 slips and 1, 25minute tie! The male was brilliant, my girls first time as the tie happened she was a little scared so I held her and reassured her and she calmed down and was fine. If they want to go again today do we allow this or absolutely not? Getting mixed advice from some pages.

Do we allow them to have another day break and meet again or do we stop?
This is my first time doing this, I'm reading different advice all over. Some people are saying to let them mate as much as they want showing signs and whatever, some are saying not to because it can be dangerous for a first time bitch As this can produce large litters? 
Also... When is the best day for a scan to confirm pregnancy? I've read different everywhere, 28days, 30 days and 36days? Thank you everyone all advice, extra advice and educating is much appreciated! I am trying my best to read and learn but different advice is everywhere!

> If they want to go again today do we allow this or absolutely not?

Today?  You've just had a 25min tie today, why do you want to try again?  You've got fresh semen where it needs to be.  The male isn't going to have any semen left and needs at least 48hours to manufacture more.  You could try again in 48 hours.  Not today.

>Do we allow them to have another day break and meet again or do we stop?

I'm assuming you haven't done any progesterone testing or timing?  There will be advantages and disadvantages.  The advantage is that, the more matings you have (every 48 hours of course, not more frequently), the better the chance of pregnancy because the more dates you are covering.  Some bitches will stand right through estrus, others will only stand when the eggs are ripe for fertilisation.  If you just breed based on receptivity and then stop, there is a risk you stop too early and before the eggs can be fertilised. 

The disadvantage is that, the more matings you do, the wider the whelping window is going to be at the end of pregnancy.  You won't know when to start your pregnancy diary from, nor when she is due to whelp.  You won't know when she has gone over.  Have a read on this forum, you will see many many posts from worried people not knowing when puppies should be appearing and if everything is still ok.  The wider your whelping window, the more uncertainty you will have at the other end.  Assuming again, that you have not done progesterone testing to determine ovulation or that you will use cytology to determine diestrus.

Only you can look at those advantages and disadvantages and decide what to do.

>some are saying not to because it can be dangerous for a first time bitch As this can produce large litters?

That is total rubbish.  The size of the litter is going to be determined by the number of eggs the bitch ovulates.  Even if this is your first time breeding a dog, you should know that basic info!!  The number of eggs that are available to be fertilised, is not going to be influenced by how many breedings you do. 

>When is the best day for a scan to confirm pregnancy?

Day 28 at the earliest.  Some scanners prefer to do a few days later.  But be warned that most dogs will start to show obvious external signs of being pregnant just 1-2 weeks after 28 days anyway, so if you can just contain yourself you will see if she is pregnant pretty soon whatever.  Consider the stress to the bitch from scanning.  And know that just because she is scanned pregnant at 28 days, doesn't mean she will whelp puppies - since dogs can absorb litters after their scans...

Thats what I thought about giving the breaks and not letting them just go at it. And of course i thought it doesn't effect the litter size But I thought to ask these questions as I'm reading other information from other pages that say different.
This is all very useful information and a good point about the whelping window.  We haven't done progesterone testing, the 2 dogs know each other (live 5 mins away) they have been enjoying each others company, playing and lazing around everyday, and only till day 13 all signs starting showing and they've really been eager.
I know they can absorb the puppies so was also a reason to ask when is best to scan as i know if done too early they may be there then gone later
Thank you for the reply

The one advantage of mating 48 hourly until teh biych goes over and is no longer receptive is that you can count backwards from tghe last mating.

A bitch will usually whelp 62+/- a day from ovuation.  It takes 2 days from ovuation fro teh eggs to be fertiliseable,a dn they will live for up to another 48 hours, at which time the bitch woudl usually be unreceptive/dog loose interest.

So in theory counting back 4/5 days from last receptive day should give you the likely whelping date.

If you stop now, your bitch may have ovuated a few days ago, or only just ovulated, some will even stand before ovuation at tehlh surge (2 days befgore ovuation).

As OneTwoThree says if you don't know when ovuation occured you could be looking at a wide whelping window, but this can happen just as easily with a single mating as with multiple matings.

In fact I had a proven bitch who was so desperate to be mated, but the male would not mate her for several days, and we thought that the one mating was enough as she had been keen for several days.  In the end she whelped 4 days  late on day 67. 

I had had her palpated at 28 days and the experienced vet was ceertain she was not as far along as mating date would indicate so I was not overly concerned when she went well overdue.