Ronalda, as a vegetarian myself, most of my soaps are without animal fats.
If your son is vegan, he may have issues with palm, as there are many people who avoid palm as much as possible for ethical reasons, even the palm from sustainable sources. If he has no issue with palm, it does add nicely to soap.
If he does have issues with palm, or you want to or need to try something else (cost, inaccessible, whatever), there are other oils to use that will produce a nice soap and some do contribute to a harder bar. Soy wax (there are several threads here at SMF with discussions about using soy wax in soap) at around 35% works pretty well for a hard bar that doesn't need to cure overly long, like a high olive oil soap does. But it may be harder to find and cost may be a factor.
Olive Oil in high percentages, up to 100% of the oils, makes a very hard bar of soap, but requires a really long cure. Castiles can be used earlier, but to reach their best potential I find an 18-month to 2-year cure is best. Some suggest 6-months, some suggest at least a year cure for high olive oil Castiles. Other high oleic oils can be used in the same way, but benefit from a longer cure.
I often use a combination of Olive (53%), Rice Bran (32%), Coconut (10%) & Shea (5%) for a very nice feeling soap and slow moving enough to do fun swirls. It's not my most favorite soap, but I do like it and the oils are easily obtained (here anyway). These are the percentages I use for swirls, but you could alter them or sub another oil to obtain characteristics you want in the soap. Sometimes I combine both Cocoa Butter & Shea Butter in equal amounts. The Cocoa Butter provides a bit more hardness than Shea Butter. Just some ideas for you.
NB: Of course always run recipes through a lye/
soap calculator.
