Tomorrow is Sunday (It would also be OK to use the future with "will" or "going to," but it's best to use the simple present since you're not making a prediction, you're stating a definite truth.) I hope ("that" is optional, in English, the phrase sounds a bit more "powerful" without "that") it's a sunny day (native speakers often use the future with "will" after "hope," but it's considered "correct" to use the present tense), because my family and I (the way you said it is not "wrong," but, as in Spanish, it's polite to mention yourself last) are going ("to go" is optional, and quite often omitted to avoid using "go" as both an auxiliary and the main verb) to the park on bicycles (plural, assuming you're not all going to ride the same bicycle.. or, you could use the adverbial phrase "by bicycle.")

By the way, I understood that you will be riding your bikes to get to the park -- if you're driving to the park, and then riding bikes, you would say "going to ride bicycles in the park." (Note the use of the preposition "in," not "to" -- you already used the preposition "to" when you said "going to ride...."

I hope you and your family had a fun afternoon!

--Phil

Tomorrow

Tomorrow will be is Sunday: the best day in the week. I hope that it will be a sunny day because I and my family my family and I are going willing to go to the park on bicycle.

Enjoy your weekend Floriano ! :)

Tomorrow

Tomorrow will be Sunday: the best day of the week. I hope it will be a sunny day because my family and I are going to go to the park on bicycle.