Dilemma about son's friend birthday

My 5 year old son got a birthday invitation for his classmate birthday party. They are doing it in mcdonald's. I have never been to such parties. They just mentioned the time and date on the invitation. My son is young so i will definetely go with him.
Is 10 dollar gift enough?
If i give a gift card will that be rude?
Is the party only for my son, or for me also?

Thanks

sailingboat, it nodoubt will be a fun party for your son. From what I understand, gifts can range between 5 - 15$ dollars. While giftcard may not be rude, buying a gift will be a nice gesture, especially kids here love to open their gifts and thank the person in the party itself (this need not happen all the time as a rule). If your child is comfortable and if the host has offered, you can drop off and pick up the child but if you stay it is not considered bad (given the age of the kids). Go prepared as not a guest for the party, it is for your son and you are just taking him. I am sure however that you will have fun too.....

Looks like it's a kiddie party. In case parents are alloed you can stay back and hang out with other parents who are waiting there.Good time to catch up with parents of your son's classmates.It's upto what you wanna give . But i wouldn't suggest giving a gift card for $10. It would be wise to buy something else for the kid. You can check for game / Story book for the b'day guy. Kids, usually are more excited in opening the presents than the present itself.

Hope this helps!

Thanks srama and sillygurl for your replies.