Oh Nutella that does sound stressful - I am utterly convinced older people must have had their genuine memories of parenting young children and babies utterly erased (perhaps over written by the reconstructed versions they have told themselves over time), they so often seem so clueless it is almost impossible to believe they were also once parents of newborns, as so many new grandparents seem to see the arrival of grandchildren and everything thereafter as all about them... so weird!
We speak English as a family language btw - this seems to have worked really well so far, but we are living in a very rural location where nobody outside the house really speaks English to or around the children, friends, extended family on DH's side etc. are all German. DH speaks German to them if they have friends here, but I still speak English to my kids and German to their friends, which seems to be fine, and they speak German to me even in front of their friends - in general DD's friends find this interesting and positive but DS1's are a bit non plussed, but neither child has ever argued or complained about it. DD's teacher says nothing marks her out as speaking German as a second language - at Kindergarten they said she mixed her articles sometimes but that many children of Kindergarten age do, but if that was an issue it fixed itself by school. When DS1 started KiGa they questioned his level of German, but the problem was actually his extreme shyness with people he doesn't know and speaking in front of groups - this has more than respolved itself now and he has no language problems. In the UK nobody could tell the kids weren't English born and bred, so so far, so good :) Who knows if they'll refuse to speak English in their teens, but I hope not!
On the school start thing, it seems to be different in each state, but:
The cut off date here in Bavaria is 30th Sept.
Using this Sept as an example - all children born before 30th Sept 2007 and not already in school are Muss Kinder - they must start school on 13th Sept unless they have an exemption. The discrepancy between the date school starts and the cut off means a few children can be aged 5 when they start school, though only for 2 weeks.
Children born between October and December 2007 are Kann Kinder - if their parents want them to start school in Sept 2013 they can take some extra tests and may be allowed to start school early. Where we live this is viewed as a ludicrous and pushy thing to do, pretty much equated with robbing your child of a childhood and dooming them to failure on all sorts of levels, but this seems to be a rural attitude - in other areas I think it is common to send children as Kann Kinder.
If children are not ready for school they can sometimes get a year's grace - this mainly seems to be used for summer born children, but it doesn't seem especially unusual for children born as early as spring to be given an extra year in Kindergarten, if there is a reason - most common seems to be maturity. Where we live pretty much all summer born boys seem to be kept back, and about half summer born girls. DD has a boy born in April 2006 in her year - she was born Sept 2007, meaning the age spread is 17 months within one school year - if there had been any Kann Kinder in her class (which there aren't) there could have been an even wider age range in one school "year" - up to about 20 months.
So most school intakes will include 5 (nearly 6) year olds with children who have already turned 7, within the same year, because of the option of holding children back.
How easy it is to hold a child back is open to interpretation though - I initially was under the impression you merely have to state your intention as a parent, but it is definitely not that easy, and there are hoops to jump through and it is ultimately down to the school whether they go with the parent's wishes or insist a child starts school. The school can also insist a child waits a year against the parents wishes - that part I already knew, as there is a girl in DD's class whom this happened to, and it seemed to have worked well - she was very immature indeed at KiGa and seemed to have some very real problems (she was still not properly toilet trained at 5) but having stayed back a year she is now doing well at school by all accounts...
That is an essay, I will log off again, still not having properly replied to people or name checked! DS2 still has a cough but no longer seems ill and miserable with it, and I have an on and off sore throat and swollen tongue (:/) but I think I am just run down so shall just plod along and ignore it - one day I shall sleep through another night, and then a few in a row (of course what I mean is DS2 will) and then, a couple of week s- and then I will glow with health and well being for ever after :o