I've only read the first few posts, but we were managing with fulltime creche (near both our offices) when DD was preschooler (so she commuted with us and we alternated doing drop off and collection, mainly DH dropping and me collecting but changing if 1 needed to stay late/arrive early on occasion). It meant we both had a chance to do extra hours if need be and we both brought work home on occasion too (and were lucky to be able to juggle diaries on most occasions she was ill, although there have been occasions where DD came into city centre bundled up in jammies, swopped car (or finisher hopped in while starter was on public transport later) and came home again for afternoon with other parent if time between meetings was short).
When she started school, DH continued to drop (getting in a bit later but staying later in evenings) and I generally manage to get back to the afterschool club in creche near home on time. I have numbers of all neighbours, few relatives nearby, and a few of DD's classmates' Mums too now in case of dire emergency - which we've used once in 3 years.
Both of us have had to do meetings overseas on occasion in the past, both pre and post DD. Generally it's 1 or the other travelling at a time (we seem to have opposite cycles, TG). DH is just as good with DD as me so either being away overnight or for a couple of nights is ok.
When DH started travelling 2 years ago for longer trips (1st was 4 weeks, most are 2-3 weeks since, with the same at home) we got an au pair to do mornings. This has evolved a little so the AP now does school drops but also collects from creche twice a week and from school twice a week (to allow afterschool activities in school, which we couldn't otherwise). I still collect from creche once a week.
What is ULTRA important though is that we keep each other informed of events and needs, and the diary on the kitchen counter is kept full with things that impact on household life (like DH going to a lecture tonight, or me needing to stay late for meetings next Monday, or dentist appointments that one of us needs to cover). And our electronic diaries also need to be kept up to date, but the kitchen one is the bible checked every night for tomorrow. As soon as notes come home, from whatever source, and for whoever, they get written in.
And being organised enough to have emergency dinners in the freezer, jars of sauce to make a fast dinner, know the nights you will need to get a takeaway (and refuse to feel guilty about it). So DD has swimming class late on Wednesdays, so she has an M&S kiddie meal or a HM meal from freezer as soon as she gets in (I try to have one that is oven-heated, so I can set it up to be ready when we walk in, otherwise microwaved type), we eat something simple to prepare either prepped as she eats and gobbled as she finishes, or once she's in bed. But on Mondays, I will have a good HM meal that I've made on Sun afternoon while doing roast dinner to just reheat the sauce and cook pasta/rice or potatoes as needed (turn on pots dinner), with a second half of that sauce frozen for another Wed or similar night. While we generally have a fairly healthy diet, we also use convenience things and know plenty of short cuts for the times they're needed.
Household must be organised, and also have my points that are important and others not (so I wash lots and throw the dry things into a basket during the week - so they are clean if needed urgently - but I only fold and iron at the weekend). And once we can find things, and are generally neat and tidy, with important areas kept clean always (kitchen surfaces, bathrooms etc), I don't worry too much about a bit of mess and dirt.
Holidays are a combination of creche, other camps at school and elsewhere (sports centre, sailing school etc), and DH and I taking our leave to suit school holidays. Not cheap, but DD seems generally happy and we've both been able to continue with our careers so far.
The one trip I had while DH was away, PIL came to stay for 3 nights (I was away 2 and v late home the 3rd) as it would have been too much responsiblity on AP. They were delighted (they live 160 miles away, as do my parents) - but it is a rarity that we call on them like that.