Kids provide motivation sure, but they also fall into ponds, scream, cut their hands, run away. It'd be easy to do something like this if you started when you only had one child or are just married but going into the bush and building a place and trying to be as self sufficient as possible is extremely difficult and costs a good bit of money to get there. Try doing this with 4 kids under 7 and a husband working full time. It'd take an insane amount of work.

I would love to be off grid in some remote location, but I'd also like to be relatively close to mass and other traditional Catholics too, the latter is more important to me.

I agree, but kids can get themselves into trouble anywhere. We started off with one, who was just 12 months old, and one due in 6 months. That was not easy, 3000kms from family and friends. With 4 under 7, that would be difficult. 

Let’s face it, we can never expect to be self-sufficient so that is not the issue. We are talking about being off-grid and this is not as expensive as many think. Of course, if you want all the city comforts that is different. It depends on your skills, imagination and ability to improvise and to do without, as illustrated in the OP.