Taking 100ug of 1p LSD should not be a strong trip, but I discourage you and your friend from taking more than that whether it's all at once or redosing after a bit.
At least for this first time with that drug.
Also, if your friend does take it with you, DO NOT allow him to redose if he says he is not feeling the effects, it is my experience that for some people the first time it might take a while to realize they are in fact high.
In fact, unless your friend is used to be around people that are high on psychedelics, it would be safer and more constructive if he stays sober, as that would give you the opportunity to explain to him how you are being affected, and he would have experienced a close person being high so he can see that a single dose of 100ug is not going to be anything drastic and could help him be at ease when and if he will try it himself.
Also, if he were to find himself in a difficult spot, I'm not positive you could provide the best support while high on a substance that is significantly different from the ones you already tried and that you are trying yourself for the first time.
With this I don't mean to be offensive, but psychedelic experiences can become really difficult moments, and even if in my personal experience the occurrence of bad trips is not high, if one is inexperienced it is more likely to not be able handle the situation in the best of ways.