It's not the breed of horse it's the horse its self and its temperament that you have to go by.
My first horse was/is an Arabian x andalusian gelding (14.3hh 4 years old, But now he's 9) he is the most quiet horse I've seen but he always gives you a challenge, he isn't brain dead .
My palomino Quarter Horse mare is so quiet she's had kids around her and sit on her and have pony rides yet she needs someone with a lot of experience.
I don't recommend first horses that are Thoroughbred or standardbred but that is my personal opinion I bet some of you are completely different.
Arabian x sounds like a good horse for you, they can go all day, good for long rides (they are used in endurance) and all sorts.
Even an Arabian x QH - Quarab.
Whatever suits you, don't always go with what other people say