Hmm. Tall order for the Spanish supermarket.
Nonetheless, at Eroski (there's one near sa Coma), there are some products available for special dietary needs. However, I'd have to say that Carrefour is much more likely to carry such things. Probable, in fact (in addition to other typical English products).
Unfortunately, the only Carrefour stores are around Palma - one just about 2km from the airport, and the other at the Valdemossa exit from the MA-20 "Via Cintura" motorway around Palma.
Are you hiring a car? If so, just take a stop at the Carrefour near the airport when you arrive. It's about 2km in the opposite direction you'd normally take to Sa Coma on the MA-19 motorway which connects with the airport. Take exit number 6 and follow the signs to "Centro Commercial". Beware this exit is always jammed with traffic. You can't miss it.