why not ask your mom to attempt a few showings if you think age may be part of the issue. How are the photos for your ads? Where are you advertising?
As much as people hate Facebook buy and sell groups I've utilized the rental groups quite a bit. I have professional photos that I use as well. You could change your ad so it says rental incentive for long term tenant to help spur more action on the ad.
Lastly try and book your showings at the same time. Last time I did some showings I tried to book 2 people per time slot and would book 15 min apart. It pushed the urgency to make a decision when people see you have other showings.
You could get people to call you during a showing if there is only one happening to make it look like people are applying. Kind of greasy but people want what others have.