Can I use regular 30 SPF on my 7 month grandson?

Look at labels. All sun blocks have age restrictions on them. Make sure you read them- buy sun block for uva and uvb rays. As always remember infants can become burned and dehydrated fairly quickly.
SPF for kids. Spf factors that range from 15 to 30 are ideal for kids. Anything much higher makes little difference in keeping children safe in the sun. It isn't necessarily harmful to use higher spf, but it may give parents a false sense of security.