Donation for the construction of the synagogue

About two and a half years ago we had a campaign for the construction of the synagogue. I undertook to raise one million shekels over 10 years. I had in mind that, with G‑d’s help, I hoped to manage to give 100,000 shekels each year. I had/still have stocks and investments, and I hoped that, with G‑d’s help, thanks to this they would continue to grow and I would be able to meet this commitment. Then, during the campaign itself, I realized that it was possible to add donors toward this sum — and indeed my brother and my brother‑in‑law also decided to join the sum.
At present, giving such amounts every year is very burdensome for my annual expenses.

Two questions:
1. Does the fact that my brother and my brother‑in‑law agreed to join change the amount I originally had in mind?
2. In any case, does the fact that it is very burdensome change anything regarding the will/intention to donate?

Thank you very much

Shalom and blessings. 

1. From the outset you included the donors toward the sum you undertook, and therefore there is no problem to include them. 

2. Even if you had not intended this from the beginning, since it is difficult for you at present, this is also a reason to permit you to recruit others to help you fulfill this commitment. 

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