When travelling with dc, fold a full set of clothes including socks and pants into a roll and secure with an elastic band. Then just hand a set to each child. No faffing about trying to find the other sock or pulling out all the clothes. Works especially well for camping.
We travel a lot and over the years have fallen into the pattern of dad first, then dc and me bringing up the rear. Never lost a child in a train or a lift and dh has a better sense of direction than I have. We do it in crowded shopping centres and on outings too. (We probably look like a family of ducks though)
Take picture on your phone of where car is parked in airport
When washing towels do an extra rinse with a cup of vinegar. The towels will be softer and you won’t have to clean the washing machine as often.
Candles and dim lamps hide a lot of dirt 
When dc were little I just used the bigger size nappy and pulled the tabs tighter on the smaller child. Worked fine.
When buying clothes for 6mts to 3 years buy 2 or 3 sets of the same outfit rather than lots of different outfits. Makes it easier to find a top/bottom that matches when they get messy and they look less like urchins.
When feeding a tot on the run, without a bib or change of clothes, take off the outer layer so that the stains can be hidden and they look less like urchins. (Yes, there’s a theme to my tips)
Not time saving at all and really a bit bonkers but I bought dd dresses in primark in several sizes and also the smallest one I could find which I cut down and cobbled into a doll dress. We had several years of her matching her dolly’s outfit at a fraction of the cost of dolly and me.
When your dc use sticker books remove the negative space piece around the stickers and the stickers will be much easier for little fingers to remove.
Put sunblock on dc from behind them rather than from the front. I have no idea why, but it’s a game changer.
To get steroid tablet into dc, melt choc button on parchment paper in microwave (5secs), crush tablet between 2 teaspoons and carefully pour onto chocolate, then fold the paper in half so the chocolate folds around the crushed medicine. Pop into freezer for 2 minutes and then feed to child.
Slice ripe banana and freeze. Zap through a blender and you have a lovely creamy “ice cream” though it has to be eaten immediately. Dc are happy to have ice cream and mum is happy cow they’re eating fruit 
When freezing, spread things out on a tray, cover and flash freeze before bagging up. This way things won’t stick together and you can reach in and grab a few easily. I do this for all sorts, eg rashers which I only buy every three months or so.