I would disagree on your definition. A convocation is a meeting, a calling together of the faithful. The Israelites were to proclaim when these meetings were.
However the command not to do servile work seems to be separate and distinct:
First day of ULB:
Lev 23:7 In the first day ye shall have an holy convocation: ye shall do no servile work therein.
Last day of ULB:
Lev 23:8 But ye shall offer an offering made by fire unto the LORD seven days: in the seventh day [is] an holy convocation: ye shall do no servile work [therein].
Pentecost:
Lev 23:21 And ye shall proclaim on the selfsame day, [that] it may be an holy convocation unto you: ye shall do no servile work [therein: it shall be] a statute for ever in all your dwellings throughout your generations.
Feast of Trumpets:
Lev 23:25 Ye shall do no servile work [therein]: but ye shall offer an offering made by fire unto the LORD.
Day of Atonement:
Lev 23:28 And ye shall do no work in that same day: for it [is] a day of atonement, to make an atonement for you before the LORD your God.
First day of feast of tabernacles:
Lev 23:35 On the first day [shall be] an holy convocation: ye shall do no servile work [therein].
Last Great Day:
Lev 23:36 Seven days ye shall offer an offering made by fire unto the LORD: on the eighth day shall be an holy convocation unto you; and ye shall offer an offering made by fire unto the LORD: it [is] a solemn assembly; [and] ye shall do no servile work [therein].
As I say, I read this to mean that Passover, while proclaimed by God to be a feast of the Lord, wasn't proclaimed to be a sabbath of rest whereas the rest of God's feast days were.