Breastfeeding baby and toddler??

When I have my second baby my son will be about 18 months. I plan on breastfeeding when he/she gets here. I didn't get to breastfeed my son due to multiple complications. Would it be weird to let him have some of my breast milk when I start producing? I thought it would be natural, but I had a family memeber tell me it was weird so I'm just wondering if its fine to do it or not. I'd pump for him since he's so used to sippy cups now. Any advice?