I work as a bouncer, I'm in plenty multiple opponent brawls often. You are getting your ass handed to you no matter what martial art if 3 people jump you. with self defense training you may last longer, you may even get away but if you try to hol dyour ground an dfight you are fucked.
LMAO @ your daughter's guard. If she ever goes to the ground with an aggressive and violent male, she is likely going to get fucked up badly unless she trains against men who are not taking it easy on her on a regular basis or is a huge bull dyke. If not, she'll go into panic mode and forget everything you ever taught her. You'd be much better off spending time with her teaching her not to be in dangerous situations and how to run like hell if she is ever in one.
I have used the Muay Thai clinch, to standing knees, to standing guillotine on more than one occasion. Works great in close quarters, and obviously puts people to sleep. One time I put someone out with the same sequence except that they hit the ground after the knees so I controlled them on the ground and quickly put them in a modified heart attack choke. Instead of going knee in armpit, I went knee to side of their neck. They went out real quick.
Additionally, the average Joe bully has no clue what to do when in a Muay Thai clinh, making elbows, knees, and trip takedowns very easy.
^^^^ And to back up what everyone else is saying, fighting 3 people with any martial art is never a good idea. Unless they are complete idiots you are going to take damage.
The best way is to street fight, fighting dirty...eye gouging, ball punching, headbutts...this is life or death sometimes fuck following a martial art 
I like BJJ as a martial arts used for self defense, but I really think only for the top game. Which makes me think wrestling is even more important than a BJJ background. You need position because like The Metal said, even if you are in the guard he can bite you, eye gouge, etc while you are working on a pass or submission. I'm not saying the guard is worthless at all, but just not the most practical. There is a statistic out there that most street fights end up on the ground, so I do believe it is important, but again, I think your position on the ground is the most important.
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Got jumped once by a group of dudes. I only did MT at the time. Guy sucker punched me, I teeped him, hit another guy with a hook... then I got grabbed, dragged to the ground and stomped beyond recognition... I think I feel a bit better knowing BJJ now(If you can keep a guy tight on you & control up close, it makes a decent shield & his stupid friends are less likely to stomp you as easily) but in my limited experience, unless you honestly believe you're gonna magically KO enough dudes that they all collectively decide to go on their way... get the fck out of there. The odds are not in your favour.