SORRY THIS GOT LONG
Well our holidays (trips/vacations etc) are dependant on DHs annual leave from work (here in Australia you're allowed 4 weeks) and our finances (whether we go away or just have an 'at home' holiday). Our children have never constrained us from going away if those two things were in favour. Of course, many children can cause financial issues
We go camping primarily, so it is a lot of stuff to pack and take, but is quite cheap. Occasionally we might do 1 or 2 nights in a motel, but it costs us a fortune with our family.
In his current job DH has to take most of his leave (3 weeks) over the Christmas/New Year period- summer over here. That is okay, but leaves only 1 week for the rest of the year.
At the moment we alternate- 1 year we will go away for a long (at least 2 weeks) holiday in summer; and stay at home for the 1 week in winter. That's what we are doing this year.
The next year we will go away for 1 week in winter, and stay at home for the summer break, or have 1 or 2 nights away in a motel. We did that last year.
We don't usually go away for long weekends (3 days) because that means being really organised to get away early Saturday (I lead kids club on Friday nights), you can't go really far because of a shorter time (don't want to spend a whole day driving for eg), everyone else in Sydney who likes camping will also be going to the same few close places (I hate crowded campsites), and then you get home and have to get everything cleaned up and packed away.
Not exactly restful, plus we don't like missing church (or DH may be preaching, leading the service etc).
Having more children does mean you have more to pack, but it's also more fun when you get there.
In regards to the length of time spent travelling (reread your post, not sure if this is what you meant)- More children makes it easier to go longer distances in the car. They can keep each other amused, pass drinks and snacks to other children etc. That's if it's going well. If they are arguing then it will be a nightmare regardless of whether you've got 2 or more children.
We don't fly for holidays because it would cost way too much for our family (although apparently flights are cheaper over there). Also you can't take all your camping gear lol.
Hope this helps