We have a potette 2in1 which can be used as a seat on a normal sized toilet or you can attach a bag and they sit on it and go in the bag which you then discard. It’s very compact which is useful. We usually ask my daughter to go for a try before we leave the house. So far she’s been ok, she’s let us know if she needs to go. But she typically only needs to go every couple of hours or so, so we’ve been lucky I think. We pack tons of spares when we go out, just in case!
Toilet just as you leave the house and as soon as you get to the destination, also if you expect to be out a few hours put underwear on, put a pull-up over it and then joggers. Tell him even though the pull-up is on he’s still to warn you about a wee/poo so you can go to the toilet. Make a friend as soon as you get to the toddler group so you have someone to watch baby while you sprint to the loos! The pull up trick saved my sanity, I was so frustrated at the wet clothes/wee filled socks and trainers and only heard about this hack from the health visitor!! Good luck x
Take plenty of spare clothes but before leaving house get them to try for a wee and once you get to the destination etc.