Is it inappropriate to get a Father's Day gift for your boyfriend who has kids from a past relationship?

I have no kids and have never dated a dad before, but am in a pretty serious relationship with my boyfriend of 6 months (I know, it's a bit soon to be serious) who is a father of two young boys (4 and 7).

I love getting him things but I don't know if it's be weird or inappropriate to get him something (I was thinking a Bass Pro gift card since he loves it but wouldn't spend his money there or give him some money in a card to go towards this boat he's saving up for) since we don't have a child together and we've been together for not a long time.

My other idea was to take him and his kiddos out for dinner, or lunch, or mini golf/something they enjoy together. But I don't want to be too much or make him uncomfortable. But I want him to know that he's a great dad and to feel appreciated.