1. The first blank follows "Mum says" and precedes "come true". The phrase "dreams come true" is a common idiom, so "dreams" is the logical word.
2. The second blank follows "and" and precedes "I want to see the Niagara Falls". Considering the context of travel and seeing landmarks, a suitable completion would be a place or a general description of what was seen.
3. Thus, the completed sentences could be: "Mum says dreams come true. ... watched nature and sights. I want to see the Niagara Falls."