I very recently started spending time with a great guy-- we've started dating, we aren't officially in a relationship yet, but that's definitely where it's headed (sometimes you know it will-- if you know what I mean.)

My question is this: He has an 18 month old son. When Father's Day rolls around, should I give him a card or something? I want to, but it seems awkward to me. Thoughts?

If it feels awkward, don't do it. As you stated, you are not in a relationship yet, so there is no reason for you to send him a card.
If you happen to talk to him on that day, wish him one verbally.

I don't understand? Why would you be giving him a card ? Isn't that what the son/daughter is supposed to give not the partner?? Sorry if I've read this wrong

Maybe it's just my family and who I know, but we do a little something for all of the fathers-- so the uncles and grandfathers and family friends get cards too, not just from their own kids. That's just what's normal for me. Mother's Day is the same. Anniversaries usually get a small present or card too, even though they aren't married to US for twenty years... lol.

It's completely acceptable for you to remember and tell him Happy Father's Day, but it is the responsibility of the child's mother to get a card from the child or do for the father.

If you spend time with them both you can help encourage the toddler to give a hug, but there is no necessity for you to get a card for him and it would be a bit over your bounds.

It's okay to remember to tell him Happy Father's Day, if you don't want to get him something, then you don't have too.