Most of the parties we have been to in ds' reception year have been at softplay. His will be there too! We have only had one party, in a hall, with an entertainer and ds hated it and was terrified of the entertainer (and i hated the entertainer, most of his jokes were aimed at the adults basically).
i think bouncy castle stuff/soft play is the best for this age group. Or craft if it's a small group and they're that sort of children!