Using one's children's investment money or taking an interest free loan to go for hajj

Q: 

1. If I am planning to go for hajj and trying to gather funds, can I use the investments I made for my kids towards my hajj? Do I have to repay it when I get back?

2. Can family members (wife/mother) give me money for hajj as an interest free loan to be repaid as I see fit when I return?

Method of embracing Islam

Q: If someone wants to revert to Islam, how do they take the shahadah? Kindly tell me those words (the shahdah) which one has to utter.

As far I know, it is like is, La ila ha illalahu mohammadur rasululah.

Are these words sufficient for the shahadah to again become a Muslim because it is basically called the first kalimah in Islam. Are there are some other words fro shahadah (for a person to again enter in Islam)?

Accepting money as a gift that was supposed to be given in charity

Q:

1. My mother wants to offer me her money which she says is earned by halaal means by selling her land. However, I have a doubt in my heart that the money is actually not halaal as it is charity collected from people that was supposed to be given to the poor and needy. Is taking this money from my mother permissible for me?

2. I want to start a business using this money, but because I have a doubt about it, I want to keep only the profits and pay back all of the invested amount to my mother. Will this be permissible?