dictionary-form + ことにする means "to decide to ～", and
dictionary-form + ～ことにしている means "I always ～", "It's my policy to ～", "I make a habit of ～ing", etc.
It's my policy to make my child take care of himself. (lit. "make my child do his own things")
Shall (we) meet at the station at 10 o'clock then?
More examples here: https://www.renshuu.org/grammar/90
させる in the first sentence is a causative form, but it's not directly related to the ことにする construction. There is no causative form in the second sentence.
dictionary-form + ことになる means "it is determined/decided/arranged that ～", "to be going to ～" (due to some external cause out of the speaker's control), "to end up ～ing", etc.
I think I'm (probably) going to make a business trip for a couple of days on the second week.
Note that he is just guessing his future. His business trip is not fixed yet, although he thinks it's very likely.