Can’t do much during this pregnancy is causing issues...

So tomorrow I’ll be 17 weeks pregnant with twins. This is my 4th successful pregnancy. I’m having di/di twins so I’m high risk but not super high risk. Anyways my ex husbands gf invited me to go tubing down the Saco River in July. I’ll be 25 weeks and I told her it’s probably not a good idea I don’t want to risk A) being 2 hours from my hospital and B) getting hurt while tubing. Not to mention I’m probably not gonna be comfortable lol. She also invited me and fiancé to go to 6flags with them this summer. Again it’s a 2 hour drive and I can’t even enjoy myself. I appreciate inviting me and I’ve told her that but I really can’t do these things. Well my ex told me he feels I’m rubbing my pregnancy in her face and that he doesn’t understand why I can’t go on family outings like I normally do. Like as if I’m using my pregnancy as an excuse. We all get along an have a wonderful relationship so it sucks that they are so upset with me and aren’t understanding that this isn’t like my other 3 non high risk pregnancies. My exes gf has also suffered from 3 or 4 miscarriages in the last 2 years and I’ve been there through it all with her. I was so scared to tell her I was pregnant this time cause I didn’t want to hurt her. And now I’m starting to feel like my pregnancy is hurting her and the more I can’t do thing the more she’s going to resent me :( I just don’t know what to do. I told them I’d rather go to the amusement park that’s only 20 min from us cause it’s closer and not as large as 6flags and that I’m down to go to the lake or beach I just don’t feel safe tubing. Am I being overly cautious or should they meet me half of ways on how to spend our summer with the kids?