I think this is one of those things where you have to get firmer. Explain to them your expectations and what will happen if they don't do as they are told before you leave. Explain to them it's not safe or acceptable to be over giddy and out of control. Then if they are running off, getting too giddy, not listening when out and about I would give them a warning and tell them to calm down and then that's it, no more, make them hold your hand. Yes they will scream, refuse to walk etc etc but you can't give in. It will be hard but of you step it up now you will reap the rewards.
I am feeling a little out of control with 4.5yo DD & her disobedience. The problem is made worse by having a 2.5yo as well - they goad each other on (when they're not fighting, although they are often adorable together).
I don't like to have 2.5yo dd in the pram all the time, when she's quite happy to trot into town, or scoot, but when the two of them are together, they would try the patience of a saint - giddy, uncontrollable & utterly uncaring of anything I say.
I don't want to just keep dd2 in the pram (until she is 15?), so can anyone share their cunning - and sustainable -tactics for going into town with two small children & not just lying down on the ground & weeping?