I'm seeing on the Good Sam trip planner that there are low clearances on I-190 (Robert Moses Parkway) and RV restrictions on same Parkway. Heard there was parking for campers passing through on Goat I...
X2 on Four Mile Creek if you can spare an overnight. Nice state park for families, and by staying there you get free parking at Niagara Falls on the US side since it is also a state park. Electric sites, water available in the park, dump station. Right on Lake Ontario so you can take scenic strolls.