would be nice? will be nice?

[keannu]

In second conditional, "would" is used for impossible or unlikely situations, and whether a condition is impossible or unlikely wholly depends on the attitude of speakers.
Sometimes, however, I find some usage that is very likely from general stand point of view, but is using "would". In the below example, "will" can be expected, as parents would be willing to do help children get on and off, but is it the writer's assumption they may not?
In to-infinitive sentences implying if clause, are they always followed by "would" regardless of its feasibility or not?

Roller coaster instruction broadcasting at an amusement park
For a fun and safe roller coaster ride, it's important to follow the rules. First, all passengers must be tall enough to ride the roller coaster. You must be at least 125 centimeters tall. Also, if you weigh more than 120 kilograms, please consult the safety guard for special instructions. Finally, it would be nice of passengers to help children get on and off the roller coaster.

 

[5jj]

Keannu, you are posting a stream of questions about uses of would that appear illogical to you.
Part of your problem, I think, is that you appear to believe that there are three types of conditional sentences, and that would should be used in a way that is consistent with those three.

The system of three conditionals (or five, if you include mixed and zero conditional) is simply a way in which some teachers and materials introduce conditional sentences to learners.

In fact, all of the below, and many others, are possible English sentences.

1. If you would like to take a seat, I will let Mr Bull know you’re here.
2. If you didn't finish up your pudding, you won't want any chocolate, then?
3. If I had known that Scrivener was giving the lecture tomorrow, I would have gone.
4. As children we were always outdoors. If it was fine, we would walk for miles.
5. When we were first married, if Andrea cooked, I would wash up.
6. If it were fine tomorrow, we would have a barbecue.
7. If they wouldn’t give us a rise, we would take strike action.
8. If Phil is playing football instead of washing up, I´m going to stop his pocket money.
9. If you pour oil in water, it will float.
10 If you pour oil in water, it floats.
11. If you have finished, start reading the next chapter.

Some of these do not fit into traditional patterns, but are all acceptable English, in the right context.

Try to get away from the ‘three conditionals’ idea, or you will forever be finding ‘exceptions’.

These articles may give you some fresh ideas:

http://www.gramorak.com/Articles/Conditionals.pdf
http://www.gramorak.com/Articles/If.pdf