Here's a brief summary of Lingua Latina grammar up to lesson 15:
1 Singular, plural of nouns, declensions 1 and 2 (nominative only)
2 Masculine, feminine and neuter nouns (decl 1 and 2) (nominative only)
Nominative and genitive cases (decl 1 and 2)
3 Nominative and accusative (decl 1 and 2)
4 Vocative. Imperative and indicative of verbs.
5 Accusative and ablative (decl 1 and 2). Imperative and indicative plural of verbs.
6 Prepositions. Locative (decl 1 and 2). Active and passive verbs (3rd person present)
7 Dative (decl 1 and 2).
8 Pronouns: quis, qui, is, ille, hic â€“ all cases
9 All cases of 1st and 2nd declension nouns and pastor (3rd declension)
10 Infinitive, active and passive. 3rd declension: leo, homo, vox and pes.
11 3rd declension neuters: corpus, flumen, mare, animal. Infinitive and accusative.
12 4th declension: exercitus. 1st, 2nd, and 3rd declension adjectives.
Comparative of adjectives.
13 5th declension: dies. Superlative of adjectives.
14 Present participle.
15 Full present tense of conjugations 1, 2, 3 and 4.
I think you should go for it. If you went up to chapter 20 of D'Ooge you've covered much of that grammar. I'm sure you can catch up.
Lingua Latina is really good!