It's hard to comment without knowing what skills are in the routine. Overall it's usually better to have a routine with slightly lower difficulty that your kids can execute well and hit cleanly over a challenging routine that will look messy and is a risk of not hitting.
Assuming you are on United Scoring, I've tried to do a quick breakdown of the stunt section...
If you're looking at the scoresheet, you also need to look at the level appropriate skills list for the division. To score difficulty in the highest range you need to have a minimum of four different level appropriate skills performed by your MOST groups - this number varies depending on the amount of athletes on the floor, but for a team of 25 for example you would need 5 groups, performing four LA skills either rippled or synchronised throughout the routine without recycling athletes. That sticks you in the top range for difficulty which is 4.5. These need to be controlled - if the judge isn't sure what the skill is supposed to be then it won't count. We had timing issues in our pyramid last year at Summit and took a huge hit to pyramid difficulty because the judges said they couldn't identify the individual skills clearly enough to score them.
Then you need to look at drivers. The judge takes each individual skill and say "OK, was it an advanced skill, or an elite skill" - and then score accordingly - 0.1 for an advanced skill or 0.2 for an elite. They also have a driver for max participation and to max that your example team of 25 would need an elite skill performed by six groups to max out this driver and score a full 0.7.
Execution is where the stunt score can really take a hit as its basically a deduction system in all but name. You start with 4 and the judges start chipping away 0.1-0.3 for each area (top person, bases/spotters, transitions, synchronisation) based on lack of technical execution. This can be things as basic as flyers legs not being locked in the air or bases moving their feet too much under the stunt.
Total stunt score is out of 10 - 4.5 max for difficulty, 4 max for execution, and 1.5 max for difficulty drivers.
For level three, an example of elite skills would be a ball up from gut to prep heel stretch, a full up to two foot extension, 1/2 twist inversion from ground to extended BP (scale, arabesque, heel stretch etc) and a full twist cradle. Advanced skills would be a ball to prep lib (no BP), 1/2 twist inversion to extended lib (no BP), full up to prep BP, etc etc.
Hope this has been some help! You really need to look at the scoresheet, the actual scoring rubric and the level appropriate skills lists altogether to figure it all out. Please trust in your coach though. They will know what they are doing and will be giving your kids the most competitive routine they can confidently hit.