Traveling with an infant

Hello I'm not sure if this is a right group to post this or not, but anyways I'd love to know a few things with traveling with and 8 month old.

We are staying with my family for 2 weeks.

1. For his formula do I just pack some in our checked bag?? Because we don't really wanna buy it when we are there unless we absolutely have to but I get WIC so I'd rather just bring some.

2. What are some things I should make sure I bring???

3. My mom has a room with a bed for us to stay, but should I bring pack n play for my son to sleep in ?? Or what did you do for baby sleep arrangements when visiting for a while??

4. We will be going to the beach , what are some must haves??

5. Any tips with flying or anything would be appreciated. We are flying American Airlines.

Answer whatever you'd like , just need some input on some things. Thanks in advance!! (No negative comments or anything please)