Good job! It sounds like you have some fun plans tomorrow. 1. You would not depict two “ss” in grandparent’s it would only have one. 2. Since you are not picking one cherry you need to make it plural “cherries.” 3. I changed it to “go” instead of “come” because you are not presently there. You are going to be there tomorrow. “Come” the subject is going to your location. “Go” is a movement to another place. 4. “Sic” is just one letter off it needs to be “six.” 5. I combined the last two sentences because “so a little excited” is not a complete sentence but can be added to the previous sentence. You need a noun and a verb and “excited” can be either a verb or an adjective. If you wanted to make it a separate sentence you could say “I am a little excited.” That way “I” would be the noun.

grandparent's=singular, grandparents'=plural

Have fun picking cherries. I haven't eaten any for a long time.

In your last sentence, you left the subject so it's ambiguous WHO is a bit excited.