1) Look for literature that meets the needs of your ensemble that has limited percussion writing. Treat selecting music the same way you would if you were low on trumpets or trombones or missing a sax section. There is literature out there! You just may have to hunt for it. (A lot of older music on the PML has lesser percussion requirements.)
2) Make sure the crucial battery instruments are covered. I always wanted the snare and bass covered first. Next would be cymbals and crucial accessories.
3) Take all the percussion parts and combine them. Have the kids cover parts when necessary. For example, the snare player can cover a few cymbal crashes and the bass drummer can cover a tambourine part. When I took my band to Midwest in 2019, I only had 6 percussionists, but played music that regularly called for 8-10 players. (No exaggeration - A lot of the newer literature calls for robust percussion sections!) We cut and paste the parts together and worked it all out in sectionals. There was one piece that had three different kids covering crash cymbals. Another had a kid running (quietly without shoes on!) to cover a timpani solo on stage right and to the crotales on stage left. Professionals do this all the time. At that point, it became a technique exercise in making all percussive sounds the same from player to player.
4) Find a wind player that can cover essential mallet or accessory parts. I once had four oboes in my band and had one cover bells and another cover claves in Moscow, 1941. They played oboe in class for most of the UIL prep period and as we got closer they transitioned to playing percussion on that piece. It was a great experience for them. Double reed players often end up in the percussion program during marching band and you can give them some early exposure now!
5) Omit parts that aren't necessary. As a TMAA judge myself, I don't penalize ensembles for missing percussion parts when I see only 2 or 3 players on stage. It's just a reality in some situations and I judge what I hear, not what's missing because of unfortunate circumstance.
In my opinion, you don't need to worry about limiting your students due to instrumentation issues. Just choose your literature wisely and work out what can be worked out!
I hope you found this post helpful!