You should try Sri Lanka .There are a lot of affordable hotels and accommodations there that will surely fit your budget and a lot of activities and nature sight seeing for both of you that you will surely enjoy.
Read below article about Sri Lanka:
Sri Lanka which is situated in the Indian Ocean grabs the attention of the visitors due to its climate and natural resources. The climate of Sri Lanka can be described as tropical and warm. The temperature may vary from 15C in the central highlands to 35C in other low areas. The monsoon rainfall occurs between the month of May and August, and between December to March in the Northeast.
Sri Lanka has an extraordinarily rich and unique bio-diversity, in fact one of the highest in Asia. Within the confines of just 65,500 square kilometres inhabit well over 600 species of terrestrial vertebrates.
There are 82 mammals (including elephant, leopard and bear), over 400 birds (the tally varies between ornithologists), 133 reptiles (including 80 snakes!), and 54 amphibians (the number rises as new species of frogs are being discovered).
This abundance of fauna is largely because in Sri Lanka's comparatively small area there are wide geological and climatic variations. The composition of Sri Lanka's fauna comprises three basic components. They are Relict species, Endemic species and Immigrant species.
Below is a link where you can check out accommodations and list of hotels in Sri Lanka:
https://www.malbeven.com/hotel/
Venice is located in Italy and it is one of the lovely and the most interesting place where you can enjoy your vacations. The most famous here is the area contains about 118 islands which are called as Sestieri they are Cannaregio, Castello, Dorsoduro, San Polo, Santa Croce and San Marco which are the best and most famous monuments.
The Venice is worth visiting during the late spring and early summer according to the climatic conditions and you can enjoy the Venice's biggest festivals in winter. The best way to enjoy the city is throwing walking, and it is only the world’s pedestrian city.
Top Attractions in Venice
? Piazza di San Marco
? Basilica di San Marco
? Campanile di San Marco
? Torre dell'Orologio
? Palazzo Ducale
? Santi Giovanni e Paolo
Lot more see and enjoy
You should come to Ireland..we have lots of cycle and walking paths and old castles!
I'm not sure where to suggest you should visit because there are so many places with nice walking trails. Have a look at this website maybe? :)
http://www.discoverireland.ie/walking
Good luck and have fun wherever you decide to go!
The lake district, theres loads of fab places.