I used to go to Venice carnevale every year from Florence when I lived in Italy in youth.
Fat Tuesday (the day before Ash Wednesday) is Feb. 9. Carnival starts about a month earlier, for every weekend, but the absolutely crazy busiest time is the last weekend before Fat Tuesday. Therefore Feb 5-7 will be a total zoo, but a lot of fun too. I would go exactly on that last weekend.
The biggest challenge will be to find accommodations. If you have not secured them already, I can only wish you good luck. I used to make my reservations in October at the latest, and sometimes all I could find was places in the Lido with no heat (and Venice is freezing in February).
If you have accommodations already, the other big challenge will be to find a free table at a restaurant. I often resigned myself to eat on the go, because the wait was too long.
If you eating on the go in the streets is not a big problem, then the other big challenge will be to manage to get on the vaporetti (water buses) which will be very crowded. I often resigned myself to just walk all over and forget about trying to get on a vaporetto.
If walking is not a problem, then the other big challenge will be the lines at the public restrooms. I often resigned myself to use bathrooms at bars. I also tried back alleys, although there are millions of people walking around at all hours of the day and night, so it was hard to do it in the canals without being noticed. I gather that you are a woman, therefore it will be even harder for you and your mother.
If all of the above are not a problem, then the other challenge is simply walking around in small alleys with millions of people trying to get through. The police tries to manage the foot traffic by alternating the directions people can walk to in an alley. This problem is particularly acute in the alleys next to Piazza San Marco. Everywhere else it's just busy (like at a mall the weekend before Christmas or for Black Friday).
If all of the above are not a problem, then you will have the best time of your life, because there is nothing like the carnival in Venice. There are basically concerts and things going on in every piazza (a piazza is actually called 'campo' or 'campiello' in Venice). And the costumes and the crazy characters showing up in the streets all dressed up in the most hilarious costumes will make it totally worthwhile. That is why I used to go every year is spite of all of the above challenges.
