I know this topic has been covered, but specifically for this summer where there is already increased summer temps and crowds, I’m wondering if Montserrat is worth a visit with a 6 and 3 year old for a day trip on a Saturday?
Sure. You already understand it'll be crowded and you're gonna have to pace yourself to the cubs' schedule, so what's the difference between being there or in hot, crowded Barcelona? Aside from getting an actual seat on the trains, the rest sounds great. And there is a trick for the return... take the cog loco down so you get on the return train before the cable car stop. Even if you have to pay another fee for that journey it'll be worth getting a seat.
We went to Montserrat a few weeks ago for a day trip from Barcelona. It was an "easy" trip to do from the city, and, to us, a fun morning.
Some background - we had intended to head up to Girona for the whole day, but the weather up there for several days was rain-rain-rain, so we went with our back-up of Montserrat which had a clear forecast for the day (as did Barcelona). We got up early to get the train and the gondola up to main level, and it was lovely. We then took the funicular up a bit & headed off for a few hikes that start/end up there. Lots of great views, some questionable trail markings, and not a ton of folks (May 12th - Tuesday) on the trails. After a couple hours, we hiked down to the main level to visit the church and Black Madonna. As we approached the line for the Black Madonna, it started to rain, but luckily, the line was undercover. We could see the rain start to really come down in the church courtyard, but we were dry as we waited (20-30mins) for our chance to see the Black Madonna. As we eventually wound our way out and then explored the church interior, the rain continued, and we noticed it was pretty socked in and we headed off to the gondola for the ride back down to the train station. MANY folks - including school groups - were still showing up, so we were pretty happy we had arrived early to beat the crowds and the heat (or rain, in our case).
To me, your idea seems like the perfect storm for an unpleasant visit, but considering a 3 & a 6 yr olds, you might be able to get in super early, see what you want to see, and get out before the crowds and heat arrive midday. Or maybe someone has visited LATE in the afternoon after most folks have come & gone? That might be a nice time to be there as the heat in addition to the crowds might have subsided quite a bit.
The biggest thing would be your expectations for what to see and do while there. The church can hold a lot of people, so a visit there is likely no worse than any other big church, but the Black Madonna line was okay for us, but probably awful at a busier time - especially with youngsters. The hiking & views (best part to me) was on pretty broad trails (sometimes steep), so even with lots of folks, you should be able to get some nice views of the surrounding area. I'd also worry a little about lines for things like the gondola and funiculars if there were lots of folks.
After reading the excellent post above, I thought I'd clarify my thoughts.
My biggest interest was in the site and the surrounding trails. It's just a beautiful setting. I didn't even have any interest in standing in line for the Black Madonna if that gives you an idea of where my brain is. So the crowds have less of an impact on my enjoyment other than the crowded train/lines to get up to the complex.
And my stuff is pretty much all outside so I would definitely have a Plan B if rain was expected that day at the site.