Welcome in both respects!
It very much sounds like the airsoft bug has bitten, believe me you’re in good company here.
You’re spot on about your first purchase and moreover you’ve actually done it the smart way by not blowing a metric shit ton o’money on your first gun, that’s a mistake many make who later realise they ain’t that into it after all and are then seen on Mack’s (you’ll see what I mean) trying to get back the grand they spent on it in the first place.
Advice wise is just enjoy it, it’s a great way to spend a day with your lad, I dare say he probably loves the fact that you play alongside him.
Its also worth remembering that most days you’ll get hit more that you’ll hit others, you’ll feel like you’ve gone a round with Bruce Lee the day after and you’ll also end up spending a few bob in addition to what you already have!
But it’s great fun and this place is absolutely golden for questions and advice, there’s some really knowledgeable players on here (not me) that are only too happy to help.
Enjoy!