OP here. DD is four. It's way too early to overschedule her and her life will not be ruined if she doesn't try everything now.
I will tell FIL it's too early to commit to a trip next year. DD seemed to have a good time and I thought it would improve her reaction to them, but sadly she went back to her old ways the next time they came by. She'll probably grow out of it or at least she'll learn to use her manners. She does better with them when I'm not around to be alpha dog parent and has probably picked up that they are happier when I'm not around so they can be grandparents and not some person who came by.
Right now I think DD does associate the activity with going away and we told her she can do it with us and sleep in her own bed. She would be taking lessons which is what FIL has offered to pay for. He wouldn't be around for it nor would he take her to the lessons. He would either be working or participating in the sport himself. So far DD has turned us down and the second sport I'm thinking of offerring her she has begged for. So I can't see her doing two sports in the fall and then suddenly dropping them fo the winter. Kids can change their mind season to season and it is up to her.
No more bean dipping. He caught me off guard. Next time I'll tell him straight out. Thank you!!
OP, glad you clarified, I was thinking DD was 12 or something. Also, the fact that FIL would not really be involved in DD's activity at all except for paying for it and knowing she was doing it (maybe coming to the occasional game?) is important to me. Again, it just reminds me of when I was a kid and I was made to do activities not because I was interested in them or because my parents really thought they were good for me, but because other family members wanted to reap the benefits (in my case, music--attending concerts, hearing me play for them at home, etc.). I was older, more like 11, and more cognizant of what was going on and that I didn't want to be doing the activities. Not that kids should get to dictate every single thing in their lives, of course, but obviously I look back on this with some bitterness.
Sometimes I like to make for/against lists... In this case, the only things that seem to be "for" the activity are that FIL would be happy and stop bugging you about it, and you wouldn't have to pay for it. There seem to be a lot more "against" reasons, such as DD being more interested in something else, you not wanting to overschedule her or schedule things too far in advance, not wanting to give in to FIL's badgering, etc.. Sounds like whatever decision you make/have made, though, you are prepared to be firm with FIL about it, so good for you.